xref: /openbmc/linux/fs/namei.c (revision 9d749629)
1 /*
2  *  linux/fs/namei.c
3  *
4  *  Copyright (C) 1991, 1992  Linus Torvalds
5  */
6 
7 /*
8  * Some corrections by tytso.
9  */
10 
11 /* [Feb 1997 T. Schoebel-Theuer] Complete rewrite of the pathname
12  * lookup logic.
13  */
14 /* [Feb-Apr 2000, AV] Rewrite to the new namespace architecture.
15  */
16 
17 #include <linux/init.h>
18 #include <linux/export.h>
19 #include <linux/kernel.h>
20 #include <linux/slab.h>
21 #include <linux/fs.h>
22 #include <linux/namei.h>
23 #include <linux/pagemap.h>
24 #include <linux/fsnotify.h>
25 #include <linux/personality.h>
26 #include <linux/security.h>
27 #include <linux/ima.h>
28 #include <linux/syscalls.h>
29 #include <linux/mount.h>
30 #include <linux/audit.h>
31 #include <linux/capability.h>
32 #include <linux/file.h>
33 #include <linux/fcntl.h>
34 #include <linux/device_cgroup.h>
35 #include <linux/fs_struct.h>
36 #include <linux/posix_acl.h>
37 #include <asm/uaccess.h>
38 
39 #include "internal.h"
40 #include "mount.h"
41 
42 /* [Feb-1997 T. Schoebel-Theuer]
43  * Fundamental changes in the pathname lookup mechanisms (namei)
44  * were necessary because of omirr.  The reason is that omirr needs
45  * to know the _real_ pathname, not the user-supplied one, in case
46  * of symlinks (and also when transname replacements occur).
47  *
48  * The new code replaces the old recursive symlink resolution with
49  * an iterative one (in case of non-nested symlink chains).  It does
50  * this with calls to <fs>_follow_link().
51  * As a side effect, dir_namei(), _namei() and follow_link() are now
52  * replaced with a single function lookup_dentry() that can handle all
53  * the special cases of the former code.
54  *
55  * With the new dcache, the pathname is stored at each inode, at least as
56  * long as the refcount of the inode is positive.  As a side effect, the
57  * size of the dcache depends on the inode cache and thus is dynamic.
58  *
59  * [29-Apr-1998 C. Scott Ananian] Updated above description of symlink
60  * resolution to correspond with current state of the code.
61  *
62  * Note that the symlink resolution is not *completely* iterative.
63  * There is still a significant amount of tail- and mid- recursion in
64  * the algorithm.  Also, note that <fs>_readlink() is not used in
65  * lookup_dentry(): lookup_dentry() on the result of <fs>_readlink()
66  * may return different results than <fs>_follow_link().  Many virtual
67  * filesystems (including /proc) exhibit this behavior.
68  */
69 
70 /* [24-Feb-97 T. Schoebel-Theuer] Side effects caused by new implementation:
71  * New symlink semantics: when open() is called with flags O_CREAT | O_EXCL
72  * and the name already exists in form of a symlink, try to create the new
73  * name indicated by the symlink. The old code always complained that the
74  * name already exists, due to not following the symlink even if its target
75  * is nonexistent.  The new semantics affects also mknod() and link() when
76  * the name is a symlink pointing to a non-existent name.
77  *
78  * I don't know which semantics is the right one, since I have no access
79  * to standards. But I found by trial that HP-UX 9.0 has the full "new"
80  * semantics implemented, while SunOS 4.1.1 and Solaris (SunOS 5.4) have the
81  * "old" one. Personally, I think the new semantics is much more logical.
82  * Note that "ln old new" where "new" is a symlink pointing to a non-existing
83  * file does succeed in both HP-UX and SunOs, but not in Solaris
84  * and in the old Linux semantics.
85  */
86 
87 /* [16-Dec-97 Kevin Buhr] For security reasons, we change some symlink
88  * semantics.  See the comments in "open_namei" and "do_link" below.
89  *
90  * [10-Sep-98 Alan Modra] Another symlink change.
91  */
92 
93 /* [Feb-Apr 2000 AV] Complete rewrite. Rules for symlinks:
94  *	inside the path - always follow.
95  *	in the last component in creation/removal/renaming - never follow.
96  *	if LOOKUP_FOLLOW passed - follow.
97  *	if the pathname has trailing slashes - follow.
98  *	otherwise - don't follow.
99  * (applied in that order).
100  *
101  * [Jun 2000 AV] Inconsistent behaviour of open() in case if flags==O_CREAT
102  * restored for 2.4. This is the last surviving part of old 4.2BSD bug.
103  * During the 2.4 we need to fix the userland stuff depending on it -
104  * hopefully we will be able to get rid of that wart in 2.5. So far only
105  * XEmacs seems to be relying on it...
106  */
107 /*
108  * [Sep 2001 AV] Single-semaphore locking scheme (kudos to David Holland)
109  * implemented.  Let's see if raised priority of ->s_vfs_rename_mutex gives
110  * any extra contention...
111  */
112 
113 /* In order to reduce some races, while at the same time doing additional
114  * checking and hopefully speeding things up, we copy filenames to the
115  * kernel data space before using them..
116  *
117  * POSIX.1 2.4: an empty pathname is invalid (ENOENT).
118  * PATH_MAX includes the nul terminator --RR.
119  */
120 void final_putname(struct filename *name)
121 {
122 	if (name->separate) {
123 		__putname(name->name);
124 		kfree(name);
125 	} else {
126 		__putname(name);
127 	}
128 }
129 
130 #define EMBEDDED_NAME_MAX	(PATH_MAX - sizeof(struct filename))
131 
132 static struct filename *
133 getname_flags(const char __user *filename, int flags, int *empty)
134 {
135 	struct filename *result, *err;
136 	int len;
137 	long max;
138 	char *kname;
139 
140 	result = audit_reusename(filename);
141 	if (result)
142 		return result;
143 
144 	result = __getname();
145 	if (unlikely(!result))
146 		return ERR_PTR(-ENOMEM);
147 
148 	/*
149 	 * First, try to embed the struct filename inside the names_cache
150 	 * allocation
151 	 */
152 	kname = (char *)result + sizeof(*result);
153 	result->name = kname;
154 	result->separate = false;
155 	max = EMBEDDED_NAME_MAX;
156 
157 recopy:
158 	len = strncpy_from_user(kname, filename, max);
159 	if (unlikely(len < 0)) {
160 		err = ERR_PTR(len);
161 		goto error;
162 	}
163 
164 	/*
165 	 * Uh-oh. We have a name that's approaching PATH_MAX. Allocate a
166 	 * separate struct filename so we can dedicate the entire
167 	 * names_cache allocation for the pathname, and re-do the copy from
168 	 * userland.
169 	 */
170 	if (len == EMBEDDED_NAME_MAX && max == EMBEDDED_NAME_MAX) {
171 		kname = (char *)result;
172 
173 		result = kzalloc(sizeof(*result), GFP_KERNEL);
174 		if (!result) {
175 			err = ERR_PTR(-ENOMEM);
176 			result = (struct filename *)kname;
177 			goto error;
178 		}
179 		result->name = kname;
180 		result->separate = true;
181 		max = PATH_MAX;
182 		goto recopy;
183 	}
184 
185 	/* The empty path is special. */
186 	if (unlikely(!len)) {
187 		if (empty)
188 			*empty = 1;
189 		err = ERR_PTR(-ENOENT);
190 		if (!(flags & LOOKUP_EMPTY))
191 			goto error;
192 	}
193 
194 	err = ERR_PTR(-ENAMETOOLONG);
195 	if (unlikely(len >= PATH_MAX))
196 		goto error;
197 
198 	result->uptr = filename;
199 	audit_getname(result);
200 	return result;
201 
202 error:
203 	final_putname(result);
204 	return err;
205 }
206 
207 struct filename *
208 getname(const char __user * filename)
209 {
210 	return getname_flags(filename, 0, NULL);
211 }
212 EXPORT_SYMBOL(getname);
213 
214 #ifdef CONFIG_AUDITSYSCALL
215 void putname(struct filename *name)
216 {
217 	if (unlikely(!audit_dummy_context()))
218 		return audit_putname(name);
219 	final_putname(name);
220 }
221 #endif
222 
223 static int check_acl(struct inode *inode, int mask)
224 {
225 #ifdef CONFIG_FS_POSIX_ACL
226 	struct posix_acl *acl;
227 
228 	if (mask & MAY_NOT_BLOCK) {
229 		acl = get_cached_acl_rcu(inode, ACL_TYPE_ACCESS);
230 	        if (!acl)
231 	                return -EAGAIN;
232 		/* no ->get_acl() calls in RCU mode... */
233 		if (acl == ACL_NOT_CACHED)
234 			return -ECHILD;
235 	        return posix_acl_permission(inode, acl, mask & ~MAY_NOT_BLOCK);
236 	}
237 
238 	acl = get_cached_acl(inode, ACL_TYPE_ACCESS);
239 
240 	/*
241 	 * A filesystem can force a ACL callback by just never filling the
242 	 * ACL cache. But normally you'd fill the cache either at inode
243 	 * instantiation time, or on the first ->get_acl call.
244 	 *
245 	 * If the filesystem doesn't have a get_acl() function at all, we'll
246 	 * just create the negative cache entry.
247 	 */
248 	if (acl == ACL_NOT_CACHED) {
249 	        if (inode->i_op->get_acl) {
250 			acl = inode->i_op->get_acl(inode, ACL_TYPE_ACCESS);
251 			if (IS_ERR(acl))
252 				return PTR_ERR(acl);
253 		} else {
254 		        set_cached_acl(inode, ACL_TYPE_ACCESS, NULL);
255 		        return -EAGAIN;
256 		}
257 	}
258 
259 	if (acl) {
260 	        int error = posix_acl_permission(inode, acl, mask);
261 	        posix_acl_release(acl);
262 	        return error;
263 	}
264 #endif
265 
266 	return -EAGAIN;
267 }
268 
269 /*
270  * This does the basic permission checking
271  */
272 static int acl_permission_check(struct inode *inode, int mask)
273 {
274 	unsigned int mode = inode->i_mode;
275 
276 	if (likely(uid_eq(current_fsuid(), inode->i_uid)))
277 		mode >>= 6;
278 	else {
279 		if (IS_POSIXACL(inode) && (mode & S_IRWXG)) {
280 			int error = check_acl(inode, mask);
281 			if (error != -EAGAIN)
282 				return error;
283 		}
284 
285 		if (in_group_p(inode->i_gid))
286 			mode >>= 3;
287 	}
288 
289 	/*
290 	 * If the DACs are ok we don't need any capability check.
291 	 */
292 	if ((mask & ~mode & (MAY_READ | MAY_WRITE | MAY_EXEC)) == 0)
293 		return 0;
294 	return -EACCES;
295 }
296 
297 /**
298  * generic_permission -  check for access rights on a Posix-like filesystem
299  * @inode:	inode to check access rights for
300  * @mask:	right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC, ...)
301  *
302  * Used to check for read/write/execute permissions on a file.
303  * We use "fsuid" for this, letting us set arbitrary permissions
304  * for filesystem access without changing the "normal" uids which
305  * are used for other things.
306  *
307  * generic_permission is rcu-walk aware. It returns -ECHILD in case an rcu-walk
308  * request cannot be satisfied (eg. requires blocking or too much complexity).
309  * It would then be called again in ref-walk mode.
310  */
311 int generic_permission(struct inode *inode, int mask)
312 {
313 	int ret;
314 
315 	/*
316 	 * Do the basic permission checks.
317 	 */
318 	ret = acl_permission_check(inode, mask);
319 	if (ret != -EACCES)
320 		return ret;
321 
322 	if (S_ISDIR(inode->i_mode)) {
323 		/* DACs are overridable for directories */
324 		if (inode_capable(inode, CAP_DAC_OVERRIDE))
325 			return 0;
326 		if (!(mask & MAY_WRITE))
327 			if (inode_capable(inode, CAP_DAC_READ_SEARCH))
328 				return 0;
329 		return -EACCES;
330 	}
331 	/*
332 	 * Read/write DACs are always overridable.
333 	 * Executable DACs are overridable when there is
334 	 * at least one exec bit set.
335 	 */
336 	if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
337 		if (inode_capable(inode, CAP_DAC_OVERRIDE))
338 			return 0;
339 
340 	/*
341 	 * Searching includes executable on directories, else just read.
342 	 */
343 	mask &= MAY_READ | MAY_WRITE | MAY_EXEC;
344 	if (mask == MAY_READ)
345 		if (inode_capable(inode, CAP_DAC_READ_SEARCH))
346 			return 0;
347 
348 	return -EACCES;
349 }
350 
351 /*
352  * We _really_ want to just do "generic_permission()" without
353  * even looking at the inode->i_op values. So we keep a cache
354  * flag in inode->i_opflags, that says "this has not special
355  * permission function, use the fast case".
356  */
357 static inline int do_inode_permission(struct inode *inode, int mask)
358 {
359 	if (unlikely(!(inode->i_opflags & IOP_FASTPERM))) {
360 		if (likely(inode->i_op->permission))
361 			return inode->i_op->permission(inode, mask);
362 
363 		/* This gets set once for the inode lifetime */
364 		spin_lock(&inode->i_lock);
365 		inode->i_opflags |= IOP_FASTPERM;
366 		spin_unlock(&inode->i_lock);
367 	}
368 	return generic_permission(inode, mask);
369 }
370 
371 /**
372  * __inode_permission - Check for access rights to a given inode
373  * @inode: Inode to check permission on
374  * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
375  *
376  * Check for read/write/execute permissions on an inode.
377  *
378  * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
379  *
380  * This does not check for a read-only file system.  You probably want
381  * inode_permission().
382  */
383 int __inode_permission(struct inode *inode, int mask)
384 {
385 	int retval;
386 
387 	if (unlikely(mask & MAY_WRITE)) {
388 		/*
389 		 * Nobody gets write access to an immutable file.
390 		 */
391 		if (IS_IMMUTABLE(inode))
392 			return -EACCES;
393 	}
394 
395 	retval = do_inode_permission(inode, mask);
396 	if (retval)
397 		return retval;
398 
399 	retval = devcgroup_inode_permission(inode, mask);
400 	if (retval)
401 		return retval;
402 
403 	return security_inode_permission(inode, mask);
404 }
405 
406 /**
407  * sb_permission - Check superblock-level permissions
408  * @sb: Superblock of inode to check permission on
409  * @inode: Inode to check permission on
410  * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
411  *
412  * Separate out file-system wide checks from inode-specific permission checks.
413  */
414 static int sb_permission(struct super_block *sb, struct inode *inode, int mask)
415 {
416 	if (unlikely(mask & MAY_WRITE)) {
417 		umode_t mode = inode->i_mode;
418 
419 		/* Nobody gets write access to a read-only fs. */
420 		if ((sb->s_flags & MS_RDONLY) &&
421 		    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
422 			return -EROFS;
423 	}
424 	return 0;
425 }
426 
427 /**
428  * inode_permission - Check for access rights to a given inode
429  * @inode: Inode to check permission on
430  * @mask: Right to check for (%MAY_READ, %MAY_WRITE, %MAY_EXEC)
431  *
432  * Check for read/write/execute permissions on an inode.  We use fs[ug]id for
433  * this, letting us set arbitrary permissions for filesystem access without
434  * changing the "normal" UIDs which are used for other things.
435  *
436  * When checking for MAY_APPEND, MAY_WRITE must also be set in @mask.
437  */
438 int inode_permission(struct inode *inode, int mask)
439 {
440 	int retval;
441 
442 	retval = sb_permission(inode->i_sb, inode, mask);
443 	if (retval)
444 		return retval;
445 	return __inode_permission(inode, mask);
446 }
447 
448 /**
449  * path_get - get a reference to a path
450  * @path: path to get the reference to
451  *
452  * Given a path increment the reference count to the dentry and the vfsmount.
453  */
454 void path_get(struct path *path)
455 {
456 	mntget(path->mnt);
457 	dget(path->dentry);
458 }
459 EXPORT_SYMBOL(path_get);
460 
461 /**
462  * path_put - put a reference to a path
463  * @path: path to put the reference to
464  *
465  * Given a path decrement the reference count to the dentry and the vfsmount.
466  */
467 void path_put(struct path *path)
468 {
469 	dput(path->dentry);
470 	mntput(path->mnt);
471 }
472 EXPORT_SYMBOL(path_put);
473 
474 /*
475  * Path walking has 2 modes, rcu-walk and ref-walk (see
476  * Documentation/filesystems/path-lookup.txt).  In situations when we can't
477  * continue in RCU mode, we attempt to drop out of rcu-walk mode and grab
478  * normal reference counts on dentries and vfsmounts to transition to rcu-walk
479  * mode.  Refcounts are grabbed at the last known good point before rcu-walk
480  * got stuck, so ref-walk may continue from there. If this is not successful
481  * (eg. a seqcount has changed), then failure is returned and it's up to caller
482  * to restart the path walk from the beginning in ref-walk mode.
483  */
484 
485 static inline void lock_rcu_walk(void)
486 {
487 	br_read_lock(&vfsmount_lock);
488 	rcu_read_lock();
489 }
490 
491 static inline void unlock_rcu_walk(void)
492 {
493 	rcu_read_unlock();
494 	br_read_unlock(&vfsmount_lock);
495 }
496 
497 /**
498  * unlazy_walk - try to switch to ref-walk mode.
499  * @nd: nameidata pathwalk data
500  * @dentry: child of nd->path.dentry or NULL
501  * Returns: 0 on success, -ECHILD on failure
502  *
503  * unlazy_walk attempts to legitimize the current nd->path, nd->root and dentry
504  * for ref-walk mode.  @dentry must be a path found by a do_lookup call on
505  * @nd or NULL.  Must be called from rcu-walk context.
506  */
507 static int unlazy_walk(struct nameidata *nd, struct dentry *dentry)
508 {
509 	struct fs_struct *fs = current->fs;
510 	struct dentry *parent = nd->path.dentry;
511 	int want_root = 0;
512 
513 	BUG_ON(!(nd->flags & LOOKUP_RCU));
514 	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
515 		want_root = 1;
516 		spin_lock(&fs->lock);
517 		if (nd->root.mnt != fs->root.mnt ||
518 				nd->root.dentry != fs->root.dentry)
519 			goto err_root;
520 	}
521 	spin_lock(&parent->d_lock);
522 	if (!dentry) {
523 		if (!__d_rcu_to_refcount(parent, nd->seq))
524 			goto err_parent;
525 		BUG_ON(nd->inode != parent->d_inode);
526 	} else {
527 		if (dentry->d_parent != parent)
528 			goto err_parent;
529 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
530 		if (!__d_rcu_to_refcount(dentry, nd->seq))
531 			goto err_child;
532 		/*
533 		 * If the sequence check on the child dentry passed, then
534 		 * the child has not been removed from its parent. This
535 		 * means the parent dentry must be valid and able to take
536 		 * a reference at this point.
537 		 */
538 		BUG_ON(!IS_ROOT(dentry) && dentry->d_parent != parent);
539 		BUG_ON(!parent->d_count);
540 		parent->d_count++;
541 		spin_unlock(&dentry->d_lock);
542 	}
543 	spin_unlock(&parent->d_lock);
544 	if (want_root) {
545 		path_get(&nd->root);
546 		spin_unlock(&fs->lock);
547 	}
548 	mntget(nd->path.mnt);
549 
550 	unlock_rcu_walk();
551 	nd->flags &= ~LOOKUP_RCU;
552 	return 0;
553 
554 err_child:
555 	spin_unlock(&dentry->d_lock);
556 err_parent:
557 	spin_unlock(&parent->d_lock);
558 err_root:
559 	if (want_root)
560 		spin_unlock(&fs->lock);
561 	return -ECHILD;
562 }
563 
564 static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
565 {
566 	return dentry->d_op->d_revalidate(dentry, flags);
567 }
568 
569 /**
570  * complete_walk - successful completion of path walk
571  * @nd:  pointer nameidata
572  *
573  * If we had been in RCU mode, drop out of it and legitimize nd->path.
574  * Revalidate the final result, unless we'd already done that during
575  * the path walk or the filesystem doesn't ask for it.  Return 0 on
576  * success, -error on failure.  In case of failure caller does not
577  * need to drop nd->path.
578  */
579 static int complete_walk(struct nameidata *nd)
580 {
581 	struct dentry *dentry = nd->path.dentry;
582 	int status;
583 
584 	if (nd->flags & LOOKUP_RCU) {
585 		nd->flags &= ~LOOKUP_RCU;
586 		if (!(nd->flags & LOOKUP_ROOT))
587 			nd->root.mnt = NULL;
588 		spin_lock(&dentry->d_lock);
589 		if (unlikely(!__d_rcu_to_refcount(dentry, nd->seq))) {
590 			spin_unlock(&dentry->d_lock);
591 			unlock_rcu_walk();
592 			return -ECHILD;
593 		}
594 		BUG_ON(nd->inode != dentry->d_inode);
595 		spin_unlock(&dentry->d_lock);
596 		mntget(nd->path.mnt);
597 		unlock_rcu_walk();
598 	}
599 
600 	if (likely(!(nd->flags & LOOKUP_JUMPED)))
601 		return 0;
602 
603 	if (likely(!(dentry->d_flags & DCACHE_OP_REVALIDATE)))
604 		return 0;
605 
606 	if (likely(!(dentry->d_sb->s_type->fs_flags & FS_REVAL_DOT)))
607 		return 0;
608 
609 	/* Note: we do not d_invalidate() */
610 	status = d_revalidate(dentry, nd->flags);
611 	if (status > 0)
612 		return 0;
613 
614 	if (!status)
615 		status = -ESTALE;
616 
617 	path_put(&nd->path);
618 	return status;
619 }
620 
621 static __always_inline void set_root(struct nameidata *nd)
622 {
623 	if (!nd->root.mnt)
624 		get_fs_root(current->fs, &nd->root);
625 }
626 
627 static int link_path_walk(const char *, struct nameidata *);
628 
629 static __always_inline void set_root_rcu(struct nameidata *nd)
630 {
631 	if (!nd->root.mnt) {
632 		struct fs_struct *fs = current->fs;
633 		unsigned seq;
634 
635 		do {
636 			seq = read_seqcount_begin(&fs->seq);
637 			nd->root = fs->root;
638 			nd->seq = __read_seqcount_begin(&nd->root.dentry->d_seq);
639 		} while (read_seqcount_retry(&fs->seq, seq));
640 	}
641 }
642 
643 static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
644 {
645 	int ret;
646 
647 	if (IS_ERR(link))
648 		goto fail;
649 
650 	if (*link == '/') {
651 		set_root(nd);
652 		path_put(&nd->path);
653 		nd->path = nd->root;
654 		path_get(&nd->root);
655 		nd->flags |= LOOKUP_JUMPED;
656 	}
657 	nd->inode = nd->path.dentry->d_inode;
658 
659 	ret = link_path_walk(link, nd);
660 	return ret;
661 fail:
662 	path_put(&nd->path);
663 	return PTR_ERR(link);
664 }
665 
666 static void path_put_conditional(struct path *path, struct nameidata *nd)
667 {
668 	dput(path->dentry);
669 	if (path->mnt != nd->path.mnt)
670 		mntput(path->mnt);
671 }
672 
673 static inline void path_to_nameidata(const struct path *path,
674 					struct nameidata *nd)
675 {
676 	if (!(nd->flags & LOOKUP_RCU)) {
677 		dput(nd->path.dentry);
678 		if (nd->path.mnt != path->mnt)
679 			mntput(nd->path.mnt);
680 	}
681 	nd->path.mnt = path->mnt;
682 	nd->path.dentry = path->dentry;
683 }
684 
685 /*
686  * Helper to directly jump to a known parsed path from ->follow_link,
687  * caller must have taken a reference to path beforehand.
688  */
689 void nd_jump_link(struct nameidata *nd, struct path *path)
690 {
691 	path_put(&nd->path);
692 
693 	nd->path = *path;
694 	nd->inode = nd->path.dentry->d_inode;
695 	nd->flags |= LOOKUP_JUMPED;
696 
697 	BUG_ON(nd->inode->i_op->follow_link);
698 }
699 
700 static inline void put_link(struct nameidata *nd, struct path *link, void *cookie)
701 {
702 	struct inode *inode = link->dentry->d_inode;
703 	if (inode->i_op->put_link)
704 		inode->i_op->put_link(link->dentry, nd, cookie);
705 	path_put(link);
706 }
707 
708 int sysctl_protected_symlinks __read_mostly = 0;
709 int sysctl_protected_hardlinks __read_mostly = 0;
710 
711 /**
712  * may_follow_link - Check symlink following for unsafe situations
713  * @link: The path of the symlink
714  * @nd: nameidata pathwalk data
715  *
716  * In the case of the sysctl_protected_symlinks sysctl being enabled,
717  * CAP_DAC_OVERRIDE needs to be specifically ignored if the symlink is
718  * in a sticky world-writable directory. This is to protect privileged
719  * processes from failing races against path names that may change out
720  * from under them by way of other users creating malicious symlinks.
721  * It will permit symlinks to be followed only when outside a sticky
722  * world-writable directory, or when the uid of the symlink and follower
723  * match, or when the directory owner matches the symlink's owner.
724  *
725  * Returns 0 if following the symlink is allowed, -ve on error.
726  */
727 static inline int may_follow_link(struct path *link, struct nameidata *nd)
728 {
729 	const struct inode *inode;
730 	const struct inode *parent;
731 
732 	if (!sysctl_protected_symlinks)
733 		return 0;
734 
735 	/* Allowed if owner and follower match. */
736 	inode = link->dentry->d_inode;
737 	if (uid_eq(current_cred()->fsuid, inode->i_uid))
738 		return 0;
739 
740 	/* Allowed if parent directory not sticky and world-writable. */
741 	parent = nd->path.dentry->d_inode;
742 	if ((parent->i_mode & (S_ISVTX|S_IWOTH)) != (S_ISVTX|S_IWOTH))
743 		return 0;
744 
745 	/* Allowed if parent directory and link owner match. */
746 	if (uid_eq(parent->i_uid, inode->i_uid))
747 		return 0;
748 
749 	audit_log_link_denied("follow_link", link);
750 	path_put_conditional(link, nd);
751 	path_put(&nd->path);
752 	return -EACCES;
753 }
754 
755 /**
756  * safe_hardlink_source - Check for safe hardlink conditions
757  * @inode: the source inode to hardlink from
758  *
759  * Return false if at least one of the following conditions:
760  *    - inode is not a regular file
761  *    - inode is setuid
762  *    - inode is setgid and group-exec
763  *    - access failure for read and write
764  *
765  * Otherwise returns true.
766  */
767 static bool safe_hardlink_source(struct inode *inode)
768 {
769 	umode_t mode = inode->i_mode;
770 
771 	/* Special files should not get pinned to the filesystem. */
772 	if (!S_ISREG(mode))
773 		return false;
774 
775 	/* Setuid files should not get pinned to the filesystem. */
776 	if (mode & S_ISUID)
777 		return false;
778 
779 	/* Executable setgid files should not get pinned to the filesystem. */
780 	if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
781 		return false;
782 
783 	/* Hardlinking to unreadable or unwritable sources is dangerous. */
784 	if (inode_permission(inode, MAY_READ | MAY_WRITE))
785 		return false;
786 
787 	return true;
788 }
789 
790 /**
791  * may_linkat - Check permissions for creating a hardlink
792  * @link: the source to hardlink from
793  *
794  * Block hardlink when all of:
795  *  - sysctl_protected_hardlinks enabled
796  *  - fsuid does not match inode
797  *  - hardlink source is unsafe (see safe_hardlink_source() above)
798  *  - not CAP_FOWNER
799  *
800  * Returns 0 if successful, -ve on error.
801  */
802 static int may_linkat(struct path *link)
803 {
804 	const struct cred *cred;
805 	struct inode *inode;
806 
807 	if (!sysctl_protected_hardlinks)
808 		return 0;
809 
810 	cred = current_cred();
811 	inode = link->dentry->d_inode;
812 
813 	/* Source inode owner (or CAP_FOWNER) can hardlink all they like,
814 	 * otherwise, it must be a safe source.
815 	 */
816 	if (uid_eq(cred->fsuid, inode->i_uid) || safe_hardlink_source(inode) ||
817 	    capable(CAP_FOWNER))
818 		return 0;
819 
820 	audit_log_link_denied("linkat", link);
821 	return -EPERM;
822 }
823 
824 static __always_inline int
825 follow_link(struct path *link, struct nameidata *nd, void **p)
826 {
827 	struct dentry *dentry = link->dentry;
828 	int error;
829 	char *s;
830 
831 	BUG_ON(nd->flags & LOOKUP_RCU);
832 
833 	if (link->mnt == nd->path.mnt)
834 		mntget(link->mnt);
835 
836 	error = -ELOOP;
837 	if (unlikely(current->total_link_count >= 40))
838 		goto out_put_nd_path;
839 
840 	cond_resched();
841 	current->total_link_count++;
842 
843 	touch_atime(link);
844 	nd_set_link(nd, NULL);
845 
846 	error = security_inode_follow_link(link->dentry, nd);
847 	if (error)
848 		goto out_put_nd_path;
849 
850 	nd->last_type = LAST_BIND;
851 	*p = dentry->d_inode->i_op->follow_link(dentry, nd);
852 	error = PTR_ERR(*p);
853 	if (IS_ERR(*p))
854 		goto out_put_nd_path;
855 
856 	error = 0;
857 	s = nd_get_link(nd);
858 	if (s) {
859 		error = __vfs_follow_link(nd, s);
860 		if (unlikely(error))
861 			put_link(nd, link, *p);
862 	}
863 
864 	return error;
865 
866 out_put_nd_path:
867 	*p = NULL;
868 	path_put(&nd->path);
869 	path_put(link);
870 	return error;
871 }
872 
873 static int follow_up_rcu(struct path *path)
874 {
875 	struct mount *mnt = real_mount(path->mnt);
876 	struct mount *parent;
877 	struct dentry *mountpoint;
878 
879 	parent = mnt->mnt_parent;
880 	if (&parent->mnt == path->mnt)
881 		return 0;
882 	mountpoint = mnt->mnt_mountpoint;
883 	path->dentry = mountpoint;
884 	path->mnt = &parent->mnt;
885 	return 1;
886 }
887 
888 /*
889  * follow_up - Find the mountpoint of path's vfsmount
890  *
891  * Given a path, find the mountpoint of its source file system.
892  * Replace @path with the path of the mountpoint in the parent mount.
893  * Up is towards /.
894  *
895  * Return 1 if we went up a level and 0 if we were already at the
896  * root.
897  */
898 int follow_up(struct path *path)
899 {
900 	struct mount *mnt = real_mount(path->mnt);
901 	struct mount *parent;
902 	struct dentry *mountpoint;
903 
904 	br_read_lock(&vfsmount_lock);
905 	parent = mnt->mnt_parent;
906 	if (parent == mnt) {
907 		br_read_unlock(&vfsmount_lock);
908 		return 0;
909 	}
910 	mntget(&parent->mnt);
911 	mountpoint = dget(mnt->mnt_mountpoint);
912 	br_read_unlock(&vfsmount_lock);
913 	dput(path->dentry);
914 	path->dentry = mountpoint;
915 	mntput(path->mnt);
916 	path->mnt = &parent->mnt;
917 	return 1;
918 }
919 
920 /*
921  * Perform an automount
922  * - return -EISDIR to tell follow_managed() to stop and return the path we
923  *   were called with.
924  */
925 static int follow_automount(struct path *path, unsigned flags,
926 			    bool *need_mntput)
927 {
928 	struct vfsmount *mnt;
929 	int err;
930 
931 	if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
932 		return -EREMOTE;
933 
934 	/* We don't want to mount if someone's just doing a stat -
935 	 * unless they're stat'ing a directory and appended a '/' to
936 	 * the name.
937 	 *
938 	 * We do, however, want to mount if someone wants to open or
939 	 * create a file of any type under the mountpoint, wants to
940 	 * traverse through the mountpoint or wants to open the
941 	 * mounted directory.  Also, autofs may mark negative dentries
942 	 * as being automount points.  These will need the attentions
943 	 * of the daemon to instantiate them before they can be used.
944 	 */
945 	if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
946 		     LOOKUP_OPEN | LOOKUP_CREATE | LOOKUP_AUTOMOUNT)) &&
947 	    path->dentry->d_inode)
948 		return -EISDIR;
949 
950 	current->total_link_count++;
951 	if (current->total_link_count >= 40)
952 		return -ELOOP;
953 
954 	mnt = path->dentry->d_op->d_automount(path);
955 	if (IS_ERR(mnt)) {
956 		/*
957 		 * The filesystem is allowed to return -EISDIR here to indicate
958 		 * it doesn't want to automount.  For instance, autofs would do
959 		 * this so that its userspace daemon can mount on this dentry.
960 		 *
961 		 * However, we can only permit this if it's a terminal point in
962 		 * the path being looked up; if it wasn't then the remainder of
963 		 * the path is inaccessible and we should say so.
964 		 */
965 		if (PTR_ERR(mnt) == -EISDIR && (flags & LOOKUP_PARENT))
966 			return -EREMOTE;
967 		return PTR_ERR(mnt);
968 	}
969 
970 	if (!mnt) /* mount collision */
971 		return 0;
972 
973 	if (!*need_mntput) {
974 		/* lock_mount() may release path->mnt on error */
975 		mntget(path->mnt);
976 		*need_mntput = true;
977 	}
978 	err = finish_automount(mnt, path);
979 
980 	switch (err) {
981 	case -EBUSY:
982 		/* Someone else made a mount here whilst we were busy */
983 		return 0;
984 	case 0:
985 		path_put(path);
986 		path->mnt = mnt;
987 		path->dentry = dget(mnt->mnt_root);
988 		return 0;
989 	default:
990 		return err;
991 	}
992 
993 }
994 
995 /*
996  * Handle a dentry that is managed in some way.
997  * - Flagged for transit management (autofs)
998  * - Flagged as mountpoint
999  * - Flagged as automount point
1000  *
1001  * This may only be called in refwalk mode.
1002  *
1003  * Serialization is taken care of in namespace.c
1004  */
1005 static int follow_managed(struct path *path, unsigned flags)
1006 {
1007 	struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
1008 	unsigned managed;
1009 	bool need_mntput = false;
1010 	int ret = 0;
1011 
1012 	/* Given that we're not holding a lock here, we retain the value in a
1013 	 * local variable for each dentry as we look at it so that we don't see
1014 	 * the components of that value change under us */
1015 	while (managed = ACCESS_ONCE(path->dentry->d_flags),
1016 	       managed &= DCACHE_MANAGED_DENTRY,
1017 	       unlikely(managed != 0)) {
1018 		/* Allow the filesystem to manage the transit without i_mutex
1019 		 * being held. */
1020 		if (managed & DCACHE_MANAGE_TRANSIT) {
1021 			BUG_ON(!path->dentry->d_op);
1022 			BUG_ON(!path->dentry->d_op->d_manage);
1023 			ret = path->dentry->d_op->d_manage(path->dentry, false);
1024 			if (ret < 0)
1025 				break;
1026 		}
1027 
1028 		/* Transit to a mounted filesystem. */
1029 		if (managed & DCACHE_MOUNTED) {
1030 			struct vfsmount *mounted = lookup_mnt(path);
1031 			if (mounted) {
1032 				dput(path->dentry);
1033 				if (need_mntput)
1034 					mntput(path->mnt);
1035 				path->mnt = mounted;
1036 				path->dentry = dget(mounted->mnt_root);
1037 				need_mntput = true;
1038 				continue;
1039 			}
1040 
1041 			/* Something is mounted on this dentry in another
1042 			 * namespace and/or whatever was mounted there in this
1043 			 * namespace got unmounted before we managed to get the
1044 			 * vfsmount_lock */
1045 		}
1046 
1047 		/* Handle an automount point */
1048 		if (managed & DCACHE_NEED_AUTOMOUNT) {
1049 			ret = follow_automount(path, flags, &need_mntput);
1050 			if (ret < 0)
1051 				break;
1052 			continue;
1053 		}
1054 
1055 		/* We didn't change the current path point */
1056 		break;
1057 	}
1058 
1059 	if (need_mntput && path->mnt == mnt)
1060 		mntput(path->mnt);
1061 	if (ret == -EISDIR)
1062 		ret = 0;
1063 	return ret < 0 ? ret : need_mntput;
1064 }
1065 
1066 int follow_down_one(struct path *path)
1067 {
1068 	struct vfsmount *mounted;
1069 
1070 	mounted = lookup_mnt(path);
1071 	if (mounted) {
1072 		dput(path->dentry);
1073 		mntput(path->mnt);
1074 		path->mnt = mounted;
1075 		path->dentry = dget(mounted->mnt_root);
1076 		return 1;
1077 	}
1078 	return 0;
1079 }
1080 
1081 static inline bool managed_dentry_might_block(struct dentry *dentry)
1082 {
1083 	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
1084 		dentry->d_op->d_manage(dentry, true) < 0);
1085 }
1086 
1087 /*
1088  * Try to skip to top of mountpoint pile in rcuwalk mode.  Fail if
1089  * we meet a managed dentry that would need blocking.
1090  */
1091 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
1092 			       struct inode **inode)
1093 {
1094 	for (;;) {
1095 		struct mount *mounted;
1096 		/*
1097 		 * Don't forget we might have a non-mountpoint managed dentry
1098 		 * that wants to block transit.
1099 		 */
1100 		if (unlikely(managed_dentry_might_block(path->dentry)))
1101 			return false;
1102 
1103 		if (!d_mountpoint(path->dentry))
1104 			break;
1105 
1106 		mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1107 		if (!mounted)
1108 			break;
1109 		path->mnt = &mounted->mnt;
1110 		path->dentry = mounted->mnt.mnt_root;
1111 		nd->flags |= LOOKUP_JUMPED;
1112 		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1113 		/*
1114 		 * Update the inode too. We don't need to re-check the
1115 		 * dentry sequence number here after this d_inode read,
1116 		 * because a mount-point is always pinned.
1117 		 */
1118 		*inode = path->dentry->d_inode;
1119 	}
1120 	return true;
1121 }
1122 
1123 static void follow_mount_rcu(struct nameidata *nd)
1124 {
1125 	while (d_mountpoint(nd->path.dentry)) {
1126 		struct mount *mounted;
1127 		mounted = __lookup_mnt(nd->path.mnt, nd->path.dentry, 1);
1128 		if (!mounted)
1129 			break;
1130 		nd->path.mnt = &mounted->mnt;
1131 		nd->path.dentry = mounted->mnt.mnt_root;
1132 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1133 	}
1134 }
1135 
1136 static int follow_dotdot_rcu(struct nameidata *nd)
1137 {
1138 	set_root_rcu(nd);
1139 
1140 	while (1) {
1141 		if (nd->path.dentry == nd->root.dentry &&
1142 		    nd->path.mnt == nd->root.mnt) {
1143 			break;
1144 		}
1145 		if (nd->path.dentry != nd->path.mnt->mnt_root) {
1146 			struct dentry *old = nd->path.dentry;
1147 			struct dentry *parent = old->d_parent;
1148 			unsigned seq;
1149 
1150 			seq = read_seqcount_begin(&parent->d_seq);
1151 			if (read_seqcount_retry(&old->d_seq, nd->seq))
1152 				goto failed;
1153 			nd->path.dentry = parent;
1154 			nd->seq = seq;
1155 			break;
1156 		}
1157 		if (!follow_up_rcu(&nd->path))
1158 			break;
1159 		nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
1160 	}
1161 	follow_mount_rcu(nd);
1162 	nd->inode = nd->path.dentry->d_inode;
1163 	return 0;
1164 
1165 failed:
1166 	nd->flags &= ~LOOKUP_RCU;
1167 	if (!(nd->flags & LOOKUP_ROOT))
1168 		nd->root.mnt = NULL;
1169 	unlock_rcu_walk();
1170 	return -ECHILD;
1171 }
1172 
1173 /*
1174  * Follow down to the covering mount currently visible to userspace.  At each
1175  * point, the filesystem owning that dentry may be queried as to whether the
1176  * caller is permitted to proceed or not.
1177  */
1178 int follow_down(struct path *path)
1179 {
1180 	unsigned managed;
1181 	int ret;
1182 
1183 	while (managed = ACCESS_ONCE(path->dentry->d_flags),
1184 	       unlikely(managed & DCACHE_MANAGED_DENTRY)) {
1185 		/* Allow the filesystem to manage the transit without i_mutex
1186 		 * being held.
1187 		 *
1188 		 * We indicate to the filesystem if someone is trying to mount
1189 		 * something here.  This gives autofs the chance to deny anyone
1190 		 * other than its daemon the right to mount on its
1191 		 * superstructure.
1192 		 *
1193 		 * The filesystem may sleep at this point.
1194 		 */
1195 		if (managed & DCACHE_MANAGE_TRANSIT) {
1196 			BUG_ON(!path->dentry->d_op);
1197 			BUG_ON(!path->dentry->d_op->d_manage);
1198 			ret = path->dentry->d_op->d_manage(
1199 				path->dentry, false);
1200 			if (ret < 0)
1201 				return ret == -EISDIR ? 0 : ret;
1202 		}
1203 
1204 		/* Transit to a mounted filesystem. */
1205 		if (managed & DCACHE_MOUNTED) {
1206 			struct vfsmount *mounted = lookup_mnt(path);
1207 			if (!mounted)
1208 				break;
1209 			dput(path->dentry);
1210 			mntput(path->mnt);
1211 			path->mnt = mounted;
1212 			path->dentry = dget(mounted->mnt_root);
1213 			continue;
1214 		}
1215 
1216 		/* Don't handle automount points here */
1217 		break;
1218 	}
1219 	return 0;
1220 }
1221 
1222 /*
1223  * Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
1224  */
1225 static void follow_mount(struct path *path)
1226 {
1227 	while (d_mountpoint(path->dentry)) {
1228 		struct vfsmount *mounted = lookup_mnt(path);
1229 		if (!mounted)
1230 			break;
1231 		dput(path->dentry);
1232 		mntput(path->mnt);
1233 		path->mnt = mounted;
1234 		path->dentry = dget(mounted->mnt_root);
1235 	}
1236 }
1237 
1238 static void follow_dotdot(struct nameidata *nd)
1239 {
1240 	set_root(nd);
1241 
1242 	while(1) {
1243 		struct dentry *old = nd->path.dentry;
1244 
1245 		if (nd->path.dentry == nd->root.dentry &&
1246 		    nd->path.mnt == nd->root.mnt) {
1247 			break;
1248 		}
1249 		if (nd->path.dentry != nd->path.mnt->mnt_root) {
1250 			/* rare case of legitimate dget_parent()... */
1251 			nd->path.dentry = dget_parent(nd->path.dentry);
1252 			dput(old);
1253 			break;
1254 		}
1255 		if (!follow_up(&nd->path))
1256 			break;
1257 	}
1258 	follow_mount(&nd->path);
1259 	nd->inode = nd->path.dentry->d_inode;
1260 }
1261 
1262 /*
1263  * This looks up the name in dcache, possibly revalidates the old dentry and
1264  * allocates a new one if not found or not valid.  In the need_lookup argument
1265  * returns whether i_op->lookup is necessary.
1266  *
1267  * dir->d_inode->i_mutex must be held
1268  */
1269 static struct dentry *lookup_dcache(struct qstr *name, struct dentry *dir,
1270 				    unsigned int flags, bool *need_lookup)
1271 {
1272 	struct dentry *dentry;
1273 	int error;
1274 
1275 	*need_lookup = false;
1276 	dentry = d_lookup(dir, name);
1277 	if (dentry) {
1278 		if (dentry->d_flags & DCACHE_OP_REVALIDATE) {
1279 			error = d_revalidate(dentry, flags);
1280 			if (unlikely(error <= 0)) {
1281 				if (error < 0) {
1282 					dput(dentry);
1283 					return ERR_PTR(error);
1284 				} else if (!d_invalidate(dentry)) {
1285 					dput(dentry);
1286 					dentry = NULL;
1287 				}
1288 			}
1289 		}
1290 	}
1291 
1292 	if (!dentry) {
1293 		dentry = d_alloc(dir, name);
1294 		if (unlikely(!dentry))
1295 			return ERR_PTR(-ENOMEM);
1296 
1297 		*need_lookup = true;
1298 	}
1299 	return dentry;
1300 }
1301 
1302 /*
1303  * Call i_op->lookup on the dentry.  The dentry must be negative but may be
1304  * hashed if it was pouplated with DCACHE_NEED_LOOKUP.
1305  *
1306  * dir->d_inode->i_mutex must be held
1307  */
1308 static struct dentry *lookup_real(struct inode *dir, struct dentry *dentry,
1309 				  unsigned int flags)
1310 {
1311 	struct dentry *old;
1312 
1313 	/* Don't create child dentry for a dead directory. */
1314 	if (unlikely(IS_DEADDIR(dir))) {
1315 		dput(dentry);
1316 		return ERR_PTR(-ENOENT);
1317 	}
1318 
1319 	old = dir->i_op->lookup(dir, dentry, flags);
1320 	if (unlikely(old)) {
1321 		dput(dentry);
1322 		dentry = old;
1323 	}
1324 	return dentry;
1325 }
1326 
1327 static struct dentry *__lookup_hash(struct qstr *name,
1328 		struct dentry *base, unsigned int flags)
1329 {
1330 	bool need_lookup;
1331 	struct dentry *dentry;
1332 
1333 	dentry = lookup_dcache(name, base, flags, &need_lookup);
1334 	if (!need_lookup)
1335 		return dentry;
1336 
1337 	return lookup_real(base->d_inode, dentry, flags);
1338 }
1339 
1340 /*
1341  *  It's more convoluted than I'd like it to be, but... it's still fairly
1342  *  small and for now I'd prefer to have fast path as straight as possible.
1343  *  It _is_ time-critical.
1344  */
1345 static int lookup_fast(struct nameidata *nd, struct qstr *name,
1346 		       struct path *path, struct inode **inode)
1347 {
1348 	struct vfsmount *mnt = nd->path.mnt;
1349 	struct dentry *dentry, *parent = nd->path.dentry;
1350 	int need_reval = 1;
1351 	int status = 1;
1352 	int err;
1353 
1354 	/*
1355 	 * Rename seqlock is not required here because in the off chance
1356 	 * of a false negative due to a concurrent rename, we're going to
1357 	 * do the non-racy lookup, below.
1358 	 */
1359 	if (nd->flags & LOOKUP_RCU) {
1360 		unsigned seq;
1361 		dentry = __d_lookup_rcu(parent, name, &seq, nd->inode);
1362 		if (!dentry)
1363 			goto unlazy;
1364 
1365 		/*
1366 		 * This sequence count validates that the inode matches
1367 		 * the dentry name information from lookup.
1368 		 */
1369 		*inode = dentry->d_inode;
1370 		if (read_seqcount_retry(&dentry->d_seq, seq))
1371 			return -ECHILD;
1372 
1373 		/*
1374 		 * This sequence count validates that the parent had no
1375 		 * changes while we did the lookup of the dentry above.
1376 		 *
1377 		 * The memory barrier in read_seqcount_begin of child is
1378 		 *  enough, we can use __read_seqcount_retry here.
1379 		 */
1380 		if (__read_seqcount_retry(&parent->d_seq, nd->seq))
1381 			return -ECHILD;
1382 		nd->seq = seq;
1383 
1384 		if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) {
1385 			status = d_revalidate(dentry, nd->flags);
1386 			if (unlikely(status <= 0)) {
1387 				if (status != -ECHILD)
1388 					need_reval = 0;
1389 				goto unlazy;
1390 			}
1391 		}
1392 		path->mnt = mnt;
1393 		path->dentry = dentry;
1394 		if (unlikely(!__follow_mount_rcu(nd, path, inode)))
1395 			goto unlazy;
1396 		if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
1397 			goto unlazy;
1398 		return 0;
1399 unlazy:
1400 		if (unlazy_walk(nd, dentry))
1401 			return -ECHILD;
1402 	} else {
1403 		dentry = __d_lookup(parent, name);
1404 	}
1405 
1406 	if (unlikely(!dentry))
1407 		goto need_lookup;
1408 
1409 	if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE) && need_reval)
1410 		status = d_revalidate(dentry, nd->flags);
1411 	if (unlikely(status <= 0)) {
1412 		if (status < 0) {
1413 			dput(dentry);
1414 			return status;
1415 		}
1416 		if (!d_invalidate(dentry)) {
1417 			dput(dentry);
1418 			goto need_lookup;
1419 		}
1420 	}
1421 
1422 	path->mnt = mnt;
1423 	path->dentry = dentry;
1424 	err = follow_managed(path, nd->flags);
1425 	if (unlikely(err < 0)) {
1426 		path_put_conditional(path, nd);
1427 		return err;
1428 	}
1429 	if (err)
1430 		nd->flags |= LOOKUP_JUMPED;
1431 	*inode = path->dentry->d_inode;
1432 	return 0;
1433 
1434 need_lookup:
1435 	return 1;
1436 }
1437 
1438 /* Fast lookup failed, do it the slow way */
1439 static int lookup_slow(struct nameidata *nd, struct qstr *name,
1440 		       struct path *path)
1441 {
1442 	struct dentry *dentry, *parent;
1443 	int err;
1444 
1445 	parent = nd->path.dentry;
1446 	BUG_ON(nd->inode != parent->d_inode);
1447 
1448 	mutex_lock(&parent->d_inode->i_mutex);
1449 	dentry = __lookup_hash(name, parent, nd->flags);
1450 	mutex_unlock(&parent->d_inode->i_mutex);
1451 	if (IS_ERR(dentry))
1452 		return PTR_ERR(dentry);
1453 	path->mnt = nd->path.mnt;
1454 	path->dentry = dentry;
1455 	err = follow_managed(path, nd->flags);
1456 	if (unlikely(err < 0)) {
1457 		path_put_conditional(path, nd);
1458 		return err;
1459 	}
1460 	if (err)
1461 		nd->flags |= LOOKUP_JUMPED;
1462 	return 0;
1463 }
1464 
1465 static inline int may_lookup(struct nameidata *nd)
1466 {
1467 	if (nd->flags & LOOKUP_RCU) {
1468 		int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
1469 		if (err != -ECHILD)
1470 			return err;
1471 		if (unlazy_walk(nd, NULL))
1472 			return -ECHILD;
1473 	}
1474 	return inode_permission(nd->inode, MAY_EXEC);
1475 }
1476 
1477 static inline int handle_dots(struct nameidata *nd, int type)
1478 {
1479 	if (type == LAST_DOTDOT) {
1480 		if (nd->flags & LOOKUP_RCU) {
1481 			if (follow_dotdot_rcu(nd))
1482 				return -ECHILD;
1483 		} else
1484 			follow_dotdot(nd);
1485 	}
1486 	return 0;
1487 }
1488 
1489 static void terminate_walk(struct nameidata *nd)
1490 {
1491 	if (!(nd->flags & LOOKUP_RCU)) {
1492 		path_put(&nd->path);
1493 	} else {
1494 		nd->flags &= ~LOOKUP_RCU;
1495 		if (!(nd->flags & LOOKUP_ROOT))
1496 			nd->root.mnt = NULL;
1497 		unlock_rcu_walk();
1498 	}
1499 }
1500 
1501 /*
1502  * Do we need to follow links? We _really_ want to be able
1503  * to do this check without having to look at inode->i_op,
1504  * so we keep a cache of "no, this doesn't need follow_link"
1505  * for the common case.
1506  */
1507 static inline int should_follow_link(struct inode *inode, int follow)
1508 {
1509 	if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
1510 		if (likely(inode->i_op->follow_link))
1511 			return follow;
1512 
1513 		/* This gets set once for the inode lifetime */
1514 		spin_lock(&inode->i_lock);
1515 		inode->i_opflags |= IOP_NOFOLLOW;
1516 		spin_unlock(&inode->i_lock);
1517 	}
1518 	return 0;
1519 }
1520 
1521 static inline int walk_component(struct nameidata *nd, struct path *path,
1522 		struct qstr *name, int type, int follow)
1523 {
1524 	struct inode *inode;
1525 	int err;
1526 	/*
1527 	 * "." and ".." are special - ".." especially so because it has
1528 	 * to be able to know about the current root directory and
1529 	 * parent relationships.
1530 	 */
1531 	if (unlikely(type != LAST_NORM))
1532 		return handle_dots(nd, type);
1533 	err = lookup_fast(nd, name, path, &inode);
1534 	if (unlikely(err)) {
1535 		if (err < 0)
1536 			goto out_err;
1537 
1538 		err = lookup_slow(nd, name, path);
1539 		if (err < 0)
1540 			goto out_err;
1541 
1542 		inode = path->dentry->d_inode;
1543 	}
1544 	err = -ENOENT;
1545 	if (!inode)
1546 		goto out_path_put;
1547 
1548 	if (should_follow_link(inode, follow)) {
1549 		if (nd->flags & LOOKUP_RCU) {
1550 			if (unlikely(unlazy_walk(nd, path->dentry))) {
1551 				err = -ECHILD;
1552 				goto out_err;
1553 			}
1554 		}
1555 		BUG_ON(inode != path->dentry->d_inode);
1556 		return 1;
1557 	}
1558 	path_to_nameidata(path, nd);
1559 	nd->inode = inode;
1560 	return 0;
1561 
1562 out_path_put:
1563 	path_to_nameidata(path, nd);
1564 out_err:
1565 	terminate_walk(nd);
1566 	return err;
1567 }
1568 
1569 /*
1570  * This limits recursive symlink follows to 8, while
1571  * limiting consecutive symlinks to 40.
1572  *
1573  * Without that kind of total limit, nasty chains of consecutive
1574  * symlinks can cause almost arbitrarily long lookups.
1575  */
1576 static inline int nested_symlink(struct path *path, struct nameidata *nd)
1577 {
1578 	int res;
1579 
1580 	if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
1581 		path_put_conditional(path, nd);
1582 		path_put(&nd->path);
1583 		return -ELOOP;
1584 	}
1585 	BUG_ON(nd->depth >= MAX_NESTED_LINKS);
1586 
1587 	nd->depth++;
1588 	current->link_count++;
1589 
1590 	do {
1591 		struct path link = *path;
1592 		void *cookie;
1593 
1594 		res = follow_link(&link, nd, &cookie);
1595 		if (res)
1596 			break;
1597 		res = walk_component(nd, path, &nd->last,
1598 				     nd->last_type, LOOKUP_FOLLOW);
1599 		put_link(nd, &link, cookie);
1600 	} while (res > 0);
1601 
1602 	current->link_count--;
1603 	nd->depth--;
1604 	return res;
1605 }
1606 
1607 /*
1608  * We really don't want to look at inode->i_op->lookup
1609  * when we don't have to. So we keep a cache bit in
1610  * the inode ->i_opflags field that says "yes, we can
1611  * do lookup on this inode".
1612  */
1613 static inline int can_lookup(struct inode *inode)
1614 {
1615 	if (likely(inode->i_opflags & IOP_LOOKUP))
1616 		return 1;
1617 	if (likely(!inode->i_op->lookup))
1618 		return 0;
1619 
1620 	/* We do this once for the lifetime of the inode */
1621 	spin_lock(&inode->i_lock);
1622 	inode->i_opflags |= IOP_LOOKUP;
1623 	spin_unlock(&inode->i_lock);
1624 	return 1;
1625 }
1626 
1627 /*
1628  * We can do the critical dentry name comparison and hashing
1629  * operations one word at a time, but we are limited to:
1630  *
1631  * - Architectures with fast unaligned word accesses. We could
1632  *   do a "get_unaligned()" if this helps and is sufficiently
1633  *   fast.
1634  *
1635  * - Little-endian machines (so that we can generate the mask
1636  *   of low bytes efficiently). Again, we *could* do a byte
1637  *   swapping load on big-endian architectures if that is not
1638  *   expensive enough to make the optimization worthless.
1639  *
1640  * - non-CONFIG_DEBUG_PAGEALLOC configurations (so that we
1641  *   do not trap on the (extremely unlikely) case of a page
1642  *   crossing operation.
1643  *
1644  * - Furthermore, we need an efficient 64-bit compile for the
1645  *   64-bit case in order to generate the "number of bytes in
1646  *   the final mask". Again, that could be replaced with a
1647  *   efficient population count instruction or similar.
1648  */
1649 #ifdef CONFIG_DCACHE_WORD_ACCESS
1650 
1651 #include <asm/word-at-a-time.h>
1652 
1653 #ifdef CONFIG_64BIT
1654 
1655 static inline unsigned int fold_hash(unsigned long hash)
1656 {
1657 	hash += hash >> (8*sizeof(int));
1658 	return hash;
1659 }
1660 
1661 #else	/* 32-bit case */
1662 
1663 #define fold_hash(x) (x)
1664 
1665 #endif
1666 
1667 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1668 {
1669 	unsigned long a, mask;
1670 	unsigned long hash = 0;
1671 
1672 	for (;;) {
1673 		a = load_unaligned_zeropad(name);
1674 		if (len < sizeof(unsigned long))
1675 			break;
1676 		hash += a;
1677 		hash *= 9;
1678 		name += sizeof(unsigned long);
1679 		len -= sizeof(unsigned long);
1680 		if (!len)
1681 			goto done;
1682 	}
1683 	mask = ~(~0ul << len*8);
1684 	hash += mask & a;
1685 done:
1686 	return fold_hash(hash);
1687 }
1688 EXPORT_SYMBOL(full_name_hash);
1689 
1690 /*
1691  * Calculate the length and hash of the path component, and
1692  * return the length of the component;
1693  */
1694 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1695 {
1696 	unsigned long a, b, adata, bdata, mask, hash, len;
1697 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
1698 
1699 	hash = a = 0;
1700 	len = -sizeof(unsigned long);
1701 	do {
1702 		hash = (hash + a) * 9;
1703 		len += sizeof(unsigned long);
1704 		a = load_unaligned_zeropad(name+len);
1705 		b = a ^ REPEAT_BYTE('/');
1706 	} while (!(has_zero(a, &adata, &constants) | has_zero(b, &bdata, &constants)));
1707 
1708 	adata = prep_zero_mask(a, adata, &constants);
1709 	bdata = prep_zero_mask(b, bdata, &constants);
1710 
1711 	mask = create_zero_mask(adata | bdata);
1712 
1713 	hash += a & zero_bytemask(mask);
1714 	*hashp = fold_hash(hash);
1715 
1716 	return len + find_zero(mask);
1717 }
1718 
1719 #else
1720 
1721 unsigned int full_name_hash(const unsigned char *name, unsigned int len)
1722 {
1723 	unsigned long hash = init_name_hash();
1724 	while (len--)
1725 		hash = partial_name_hash(*name++, hash);
1726 	return end_name_hash(hash);
1727 }
1728 EXPORT_SYMBOL(full_name_hash);
1729 
1730 /*
1731  * We know there's a real path component here of at least
1732  * one character.
1733  */
1734 static inline unsigned long hash_name(const char *name, unsigned int *hashp)
1735 {
1736 	unsigned long hash = init_name_hash();
1737 	unsigned long len = 0, c;
1738 
1739 	c = (unsigned char)*name;
1740 	do {
1741 		len++;
1742 		hash = partial_name_hash(c, hash);
1743 		c = (unsigned char)name[len];
1744 	} while (c && c != '/');
1745 	*hashp = end_name_hash(hash);
1746 	return len;
1747 }
1748 
1749 #endif
1750 
1751 /*
1752  * Name resolution.
1753  * This is the basic name resolution function, turning a pathname into
1754  * the final dentry. We expect 'base' to be positive and a directory.
1755  *
1756  * Returns 0 and nd will have valid dentry and mnt on success.
1757  * Returns error and drops reference to input namei data on failure.
1758  */
1759 static int link_path_walk(const char *name, struct nameidata *nd)
1760 {
1761 	struct path next;
1762 	int err;
1763 
1764 	while (*name=='/')
1765 		name++;
1766 	if (!*name)
1767 		return 0;
1768 
1769 	/* At this point we know we have a real path component. */
1770 	for(;;) {
1771 		struct qstr this;
1772 		long len;
1773 		int type;
1774 
1775 		err = may_lookup(nd);
1776  		if (err)
1777 			break;
1778 
1779 		len = hash_name(name, &this.hash);
1780 		this.name = name;
1781 		this.len = len;
1782 
1783 		type = LAST_NORM;
1784 		if (name[0] == '.') switch (len) {
1785 			case 2:
1786 				if (name[1] == '.') {
1787 					type = LAST_DOTDOT;
1788 					nd->flags |= LOOKUP_JUMPED;
1789 				}
1790 				break;
1791 			case 1:
1792 				type = LAST_DOT;
1793 		}
1794 		if (likely(type == LAST_NORM)) {
1795 			struct dentry *parent = nd->path.dentry;
1796 			nd->flags &= ~LOOKUP_JUMPED;
1797 			if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
1798 				err = parent->d_op->d_hash(parent, nd->inode,
1799 							   &this);
1800 				if (err < 0)
1801 					break;
1802 			}
1803 		}
1804 
1805 		if (!name[len])
1806 			goto last_component;
1807 		/*
1808 		 * If it wasn't NUL, we know it was '/'. Skip that
1809 		 * slash, and continue until no more slashes.
1810 		 */
1811 		do {
1812 			len++;
1813 		} while (unlikely(name[len] == '/'));
1814 		if (!name[len])
1815 			goto last_component;
1816 		name += len;
1817 
1818 		err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
1819 		if (err < 0)
1820 			return err;
1821 
1822 		if (err) {
1823 			err = nested_symlink(&next, nd);
1824 			if (err)
1825 				return err;
1826 		}
1827 		if (can_lookup(nd->inode))
1828 			continue;
1829 		err = -ENOTDIR;
1830 		break;
1831 		/* here ends the main loop */
1832 
1833 last_component:
1834 		nd->last = this;
1835 		nd->last_type = type;
1836 		return 0;
1837 	}
1838 	terminate_walk(nd);
1839 	return err;
1840 }
1841 
1842 static int path_init(int dfd, const char *name, unsigned int flags,
1843 		     struct nameidata *nd, struct file **fp)
1844 {
1845 	int retval = 0;
1846 
1847 	nd->last_type = LAST_ROOT; /* if there are only slashes... */
1848 	nd->flags = flags | LOOKUP_JUMPED;
1849 	nd->depth = 0;
1850 	if (flags & LOOKUP_ROOT) {
1851 		struct inode *inode = nd->root.dentry->d_inode;
1852 		if (*name) {
1853 			if (!can_lookup(inode))
1854 				return -ENOTDIR;
1855 			retval = inode_permission(inode, MAY_EXEC);
1856 			if (retval)
1857 				return retval;
1858 		}
1859 		nd->path = nd->root;
1860 		nd->inode = inode;
1861 		if (flags & LOOKUP_RCU) {
1862 			lock_rcu_walk();
1863 			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1864 		} else {
1865 			path_get(&nd->path);
1866 		}
1867 		return 0;
1868 	}
1869 
1870 	nd->root.mnt = NULL;
1871 
1872 	if (*name=='/') {
1873 		if (flags & LOOKUP_RCU) {
1874 			lock_rcu_walk();
1875 			set_root_rcu(nd);
1876 		} else {
1877 			set_root(nd);
1878 			path_get(&nd->root);
1879 		}
1880 		nd->path = nd->root;
1881 	} else if (dfd == AT_FDCWD) {
1882 		if (flags & LOOKUP_RCU) {
1883 			struct fs_struct *fs = current->fs;
1884 			unsigned seq;
1885 
1886 			lock_rcu_walk();
1887 
1888 			do {
1889 				seq = read_seqcount_begin(&fs->seq);
1890 				nd->path = fs->pwd;
1891 				nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1892 			} while (read_seqcount_retry(&fs->seq, seq));
1893 		} else {
1894 			get_fs_pwd(current->fs, &nd->path);
1895 		}
1896 	} else {
1897 		/* Caller must check execute permissions on the starting path component */
1898 		struct fd f = fdget_raw(dfd);
1899 		struct dentry *dentry;
1900 
1901 		if (!f.file)
1902 			return -EBADF;
1903 
1904 		dentry = f.file->f_path.dentry;
1905 
1906 		if (*name) {
1907 			if (!can_lookup(dentry->d_inode)) {
1908 				fdput(f);
1909 				return -ENOTDIR;
1910 			}
1911 		}
1912 
1913 		nd->path = f.file->f_path;
1914 		if (flags & LOOKUP_RCU) {
1915 			if (f.need_put)
1916 				*fp = f.file;
1917 			nd->seq = __read_seqcount_begin(&nd->path.dentry->d_seq);
1918 			lock_rcu_walk();
1919 		} else {
1920 			path_get(&nd->path);
1921 			fdput(f);
1922 		}
1923 	}
1924 
1925 	nd->inode = nd->path.dentry->d_inode;
1926 	return 0;
1927 }
1928 
1929 static inline int lookup_last(struct nameidata *nd, struct path *path)
1930 {
1931 	if (nd->last_type == LAST_NORM && nd->last.name[nd->last.len])
1932 		nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
1933 
1934 	nd->flags &= ~LOOKUP_PARENT;
1935 	return walk_component(nd, path, &nd->last, nd->last_type,
1936 					nd->flags & LOOKUP_FOLLOW);
1937 }
1938 
1939 /* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
1940 static int path_lookupat(int dfd, const char *name,
1941 				unsigned int flags, struct nameidata *nd)
1942 {
1943 	struct file *base = NULL;
1944 	struct path path;
1945 	int err;
1946 
1947 	/*
1948 	 * Path walking is largely split up into 2 different synchronisation
1949 	 * schemes, rcu-walk and ref-walk (explained in
1950 	 * Documentation/filesystems/path-lookup.txt). These share much of the
1951 	 * path walk code, but some things particularly setup, cleanup, and
1952 	 * following mounts are sufficiently divergent that functions are
1953 	 * duplicated. Typically there is a function foo(), and its RCU
1954 	 * analogue, foo_rcu().
1955 	 *
1956 	 * -ECHILD is the error number of choice (just to avoid clashes) that
1957 	 * is returned if some aspect of an rcu-walk fails. Such an error must
1958 	 * be handled by restarting a traditional ref-walk (which will always
1959 	 * be able to complete).
1960 	 */
1961 	err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base);
1962 
1963 	if (unlikely(err))
1964 		return err;
1965 
1966 	current->total_link_count = 0;
1967 	err = link_path_walk(name, nd);
1968 
1969 	if (!err && !(flags & LOOKUP_PARENT)) {
1970 		err = lookup_last(nd, &path);
1971 		while (err > 0) {
1972 			void *cookie;
1973 			struct path link = path;
1974 			err = may_follow_link(&link, nd);
1975 			if (unlikely(err))
1976 				break;
1977 			nd->flags |= LOOKUP_PARENT;
1978 			err = follow_link(&link, nd, &cookie);
1979 			if (err)
1980 				break;
1981 			err = lookup_last(nd, &path);
1982 			put_link(nd, &link, cookie);
1983 		}
1984 	}
1985 
1986 	if (!err)
1987 		err = complete_walk(nd);
1988 
1989 	if (!err && nd->flags & LOOKUP_DIRECTORY) {
1990 		if (!nd->inode->i_op->lookup) {
1991 			path_put(&nd->path);
1992 			err = -ENOTDIR;
1993 		}
1994 	}
1995 
1996 	if (base)
1997 		fput(base);
1998 
1999 	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT)) {
2000 		path_put(&nd->root);
2001 		nd->root.mnt = NULL;
2002 	}
2003 	return err;
2004 }
2005 
2006 static int filename_lookup(int dfd, struct filename *name,
2007 				unsigned int flags, struct nameidata *nd)
2008 {
2009 	int retval = path_lookupat(dfd, name->name, flags | LOOKUP_RCU, nd);
2010 	if (unlikely(retval == -ECHILD))
2011 		retval = path_lookupat(dfd, name->name, flags, nd);
2012 	if (unlikely(retval == -ESTALE))
2013 		retval = path_lookupat(dfd, name->name,
2014 						flags | LOOKUP_REVAL, nd);
2015 
2016 	if (likely(!retval))
2017 		audit_inode(name, nd->path.dentry, flags & LOOKUP_PARENT);
2018 	return retval;
2019 }
2020 
2021 static int do_path_lookup(int dfd, const char *name,
2022 				unsigned int flags, struct nameidata *nd)
2023 {
2024 	struct filename filename = { .name = name };
2025 
2026 	return filename_lookup(dfd, &filename, flags, nd);
2027 }
2028 
2029 /* does lookup, returns the object with parent locked */
2030 struct dentry *kern_path_locked(const char *name, struct path *path)
2031 {
2032 	struct nameidata nd;
2033 	struct dentry *d;
2034 	int err = do_path_lookup(AT_FDCWD, name, LOOKUP_PARENT, &nd);
2035 	if (err)
2036 		return ERR_PTR(err);
2037 	if (nd.last_type != LAST_NORM) {
2038 		path_put(&nd.path);
2039 		return ERR_PTR(-EINVAL);
2040 	}
2041 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
2042 	d = __lookup_hash(&nd.last, nd.path.dentry, 0);
2043 	if (IS_ERR(d)) {
2044 		mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
2045 		path_put(&nd.path);
2046 		return d;
2047 	}
2048 	*path = nd.path;
2049 	return d;
2050 }
2051 
2052 int kern_path(const char *name, unsigned int flags, struct path *path)
2053 {
2054 	struct nameidata nd;
2055 	int res = do_path_lookup(AT_FDCWD, name, flags, &nd);
2056 	if (!res)
2057 		*path = nd.path;
2058 	return res;
2059 }
2060 
2061 /**
2062  * vfs_path_lookup - lookup a file path relative to a dentry-vfsmount pair
2063  * @dentry:  pointer to dentry of the base directory
2064  * @mnt: pointer to vfs mount of the base directory
2065  * @name: pointer to file name
2066  * @flags: lookup flags
2067  * @path: pointer to struct path to fill
2068  */
2069 int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
2070 		    const char *name, unsigned int flags,
2071 		    struct path *path)
2072 {
2073 	struct nameidata nd;
2074 	int err;
2075 	nd.root.dentry = dentry;
2076 	nd.root.mnt = mnt;
2077 	BUG_ON(flags & LOOKUP_PARENT);
2078 	/* the first argument of do_path_lookup() is ignored with LOOKUP_ROOT */
2079 	err = do_path_lookup(AT_FDCWD, name, flags | LOOKUP_ROOT, &nd);
2080 	if (!err)
2081 		*path = nd.path;
2082 	return err;
2083 }
2084 
2085 /*
2086  * Restricted form of lookup. Doesn't follow links, single-component only,
2087  * needs parent already locked. Doesn't follow mounts.
2088  * SMP-safe.
2089  */
2090 static struct dentry *lookup_hash(struct nameidata *nd)
2091 {
2092 	return __lookup_hash(&nd->last, nd->path.dentry, nd->flags);
2093 }
2094 
2095 /**
2096  * lookup_one_len - filesystem helper to lookup single pathname component
2097  * @name:	pathname component to lookup
2098  * @base:	base directory to lookup from
2099  * @len:	maximum length @len should be interpreted to
2100  *
2101  * Note that this routine is purely a helper for filesystem usage and should
2102  * not be called by generic code.  Also note that by using this function the
2103  * nameidata argument is passed to the filesystem methods and a filesystem
2104  * using this helper needs to be prepared for that.
2105  */
2106 struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
2107 {
2108 	struct qstr this;
2109 	unsigned int c;
2110 	int err;
2111 
2112 	WARN_ON_ONCE(!mutex_is_locked(&base->d_inode->i_mutex));
2113 
2114 	this.name = name;
2115 	this.len = len;
2116 	this.hash = full_name_hash(name, len);
2117 	if (!len)
2118 		return ERR_PTR(-EACCES);
2119 
2120 	if (unlikely(name[0] == '.')) {
2121 		if (len < 2 || (len == 2 && name[1] == '.'))
2122 			return ERR_PTR(-EACCES);
2123 	}
2124 
2125 	while (len--) {
2126 		c = *(const unsigned char *)name++;
2127 		if (c == '/' || c == '\0')
2128 			return ERR_PTR(-EACCES);
2129 	}
2130 	/*
2131 	 * See if the low-level filesystem might want
2132 	 * to use its own hash..
2133 	 */
2134 	if (base->d_flags & DCACHE_OP_HASH) {
2135 		int err = base->d_op->d_hash(base, base->d_inode, &this);
2136 		if (err < 0)
2137 			return ERR_PTR(err);
2138 	}
2139 
2140 	err = inode_permission(base->d_inode, MAY_EXEC);
2141 	if (err)
2142 		return ERR_PTR(err);
2143 
2144 	return __lookup_hash(&this, base, 0);
2145 }
2146 
2147 int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
2148 		 struct path *path, int *empty)
2149 {
2150 	struct nameidata nd;
2151 	struct filename *tmp = getname_flags(name, flags, empty);
2152 	int err = PTR_ERR(tmp);
2153 	if (!IS_ERR(tmp)) {
2154 
2155 		BUG_ON(flags & LOOKUP_PARENT);
2156 
2157 		err = filename_lookup(dfd, tmp, flags, &nd);
2158 		putname(tmp);
2159 		if (!err)
2160 			*path = nd.path;
2161 	}
2162 	return err;
2163 }
2164 
2165 int user_path_at(int dfd, const char __user *name, unsigned flags,
2166 		 struct path *path)
2167 {
2168 	return user_path_at_empty(dfd, name, flags, path, NULL);
2169 }
2170 
2171 /*
2172  * NB: most callers don't do anything directly with the reference to the
2173  *     to struct filename, but the nd->last pointer points into the name string
2174  *     allocated by getname. So we must hold the reference to it until all
2175  *     path-walking is complete.
2176  */
2177 static struct filename *
2178 user_path_parent(int dfd, const char __user *path, struct nameidata *nd,
2179 		 unsigned int flags)
2180 {
2181 	struct filename *s = getname(path);
2182 	int error;
2183 
2184 	/* only LOOKUP_REVAL is allowed in extra flags */
2185 	flags &= LOOKUP_REVAL;
2186 
2187 	if (IS_ERR(s))
2188 		return s;
2189 
2190 	error = filename_lookup(dfd, s, flags | LOOKUP_PARENT, nd);
2191 	if (error) {
2192 		putname(s);
2193 		return ERR_PTR(error);
2194 	}
2195 
2196 	return s;
2197 }
2198 
2199 /*
2200  * It's inline, so penalty for filesystems that don't use sticky bit is
2201  * minimal.
2202  */
2203 static inline int check_sticky(struct inode *dir, struct inode *inode)
2204 {
2205 	kuid_t fsuid = current_fsuid();
2206 
2207 	if (!(dir->i_mode & S_ISVTX))
2208 		return 0;
2209 	if (uid_eq(inode->i_uid, fsuid))
2210 		return 0;
2211 	if (uid_eq(dir->i_uid, fsuid))
2212 		return 0;
2213 	return !inode_capable(inode, CAP_FOWNER);
2214 }
2215 
2216 /*
2217  *	Check whether we can remove a link victim from directory dir, check
2218  *  whether the type of victim is right.
2219  *  1. We can't do it if dir is read-only (done in permission())
2220  *  2. We should have write and exec permissions on dir
2221  *  3. We can't remove anything from append-only dir
2222  *  4. We can't do anything with immutable dir (done in permission())
2223  *  5. If the sticky bit on dir is set we should either
2224  *	a. be owner of dir, or
2225  *	b. be owner of victim, or
2226  *	c. have CAP_FOWNER capability
2227  *  6. If the victim is append-only or immutable we can't do antyhing with
2228  *     links pointing to it.
2229  *  7. If we were asked to remove a directory and victim isn't one - ENOTDIR.
2230  *  8. If we were asked to remove a non-directory and victim isn't one - EISDIR.
2231  *  9. We can't remove a root or mountpoint.
2232  * 10. We don't allow removal of NFS sillyrenamed files; it's handled by
2233  *     nfs_async_unlink().
2234  */
2235 static int may_delete(struct inode *dir,struct dentry *victim,int isdir)
2236 {
2237 	int error;
2238 
2239 	if (!victim->d_inode)
2240 		return -ENOENT;
2241 
2242 	BUG_ON(victim->d_parent->d_inode != dir);
2243 	audit_inode_child(dir, victim, AUDIT_TYPE_CHILD_DELETE);
2244 
2245 	error = inode_permission(dir, MAY_WRITE | MAY_EXEC);
2246 	if (error)
2247 		return error;
2248 	if (IS_APPEND(dir))
2249 		return -EPERM;
2250 	if (check_sticky(dir, victim->d_inode)||IS_APPEND(victim->d_inode)||
2251 	    IS_IMMUTABLE(victim->d_inode) || IS_SWAPFILE(victim->d_inode))
2252 		return -EPERM;
2253 	if (isdir) {
2254 		if (!S_ISDIR(victim->d_inode->i_mode))
2255 			return -ENOTDIR;
2256 		if (IS_ROOT(victim))
2257 			return -EBUSY;
2258 	} else if (S_ISDIR(victim->d_inode->i_mode))
2259 		return -EISDIR;
2260 	if (IS_DEADDIR(dir))
2261 		return -ENOENT;
2262 	if (victim->d_flags & DCACHE_NFSFS_RENAMED)
2263 		return -EBUSY;
2264 	return 0;
2265 }
2266 
2267 /*	Check whether we can create an object with dentry child in directory
2268  *  dir.
2269  *  1. We can't do it if child already exists (open has special treatment for
2270  *     this case, but since we are inlined it's OK)
2271  *  2. We can't do it if dir is read-only (done in permission())
2272  *  3. We should have write and exec permissions on dir
2273  *  4. We can't do it if dir is immutable (done in permission())
2274  */
2275 static inline int may_create(struct inode *dir, struct dentry *child)
2276 {
2277 	if (child->d_inode)
2278 		return -EEXIST;
2279 	if (IS_DEADDIR(dir))
2280 		return -ENOENT;
2281 	return inode_permission(dir, MAY_WRITE | MAY_EXEC);
2282 }
2283 
2284 /*
2285  * p1 and p2 should be directories on the same fs.
2286  */
2287 struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
2288 {
2289 	struct dentry *p;
2290 
2291 	if (p1 == p2) {
2292 		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2293 		return NULL;
2294 	}
2295 
2296 	mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2297 
2298 	p = d_ancestor(p2, p1);
2299 	if (p) {
2300 		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_PARENT);
2301 		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_CHILD);
2302 		return p;
2303 	}
2304 
2305 	p = d_ancestor(p1, p2);
2306 	if (p) {
2307 		mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2308 		mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2309 		return p;
2310 	}
2311 
2312 	mutex_lock_nested(&p1->d_inode->i_mutex, I_MUTEX_PARENT);
2313 	mutex_lock_nested(&p2->d_inode->i_mutex, I_MUTEX_CHILD);
2314 	return NULL;
2315 }
2316 
2317 void unlock_rename(struct dentry *p1, struct dentry *p2)
2318 {
2319 	mutex_unlock(&p1->d_inode->i_mutex);
2320 	if (p1 != p2) {
2321 		mutex_unlock(&p2->d_inode->i_mutex);
2322 		mutex_unlock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
2323 	}
2324 }
2325 
2326 int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode,
2327 		bool want_excl)
2328 {
2329 	int error = may_create(dir, dentry);
2330 	if (error)
2331 		return error;
2332 
2333 	if (!dir->i_op->create)
2334 		return -EACCES;	/* shouldn't it be ENOSYS? */
2335 	mode &= S_IALLUGO;
2336 	mode |= S_IFREG;
2337 	error = security_inode_create(dir, dentry, mode);
2338 	if (error)
2339 		return error;
2340 	error = dir->i_op->create(dir, dentry, mode, want_excl);
2341 	if (!error)
2342 		fsnotify_create(dir, dentry);
2343 	return error;
2344 }
2345 
2346 static int may_open(struct path *path, int acc_mode, int flag)
2347 {
2348 	struct dentry *dentry = path->dentry;
2349 	struct inode *inode = dentry->d_inode;
2350 	int error;
2351 
2352 	/* O_PATH? */
2353 	if (!acc_mode)
2354 		return 0;
2355 
2356 	if (!inode)
2357 		return -ENOENT;
2358 
2359 	switch (inode->i_mode & S_IFMT) {
2360 	case S_IFLNK:
2361 		return -ELOOP;
2362 	case S_IFDIR:
2363 		if (acc_mode & MAY_WRITE)
2364 			return -EISDIR;
2365 		break;
2366 	case S_IFBLK:
2367 	case S_IFCHR:
2368 		if (path->mnt->mnt_flags & MNT_NODEV)
2369 			return -EACCES;
2370 		/*FALLTHRU*/
2371 	case S_IFIFO:
2372 	case S_IFSOCK:
2373 		flag &= ~O_TRUNC;
2374 		break;
2375 	}
2376 
2377 	error = inode_permission(inode, acc_mode);
2378 	if (error)
2379 		return error;
2380 
2381 	/*
2382 	 * An append-only file must be opened in append mode for writing.
2383 	 */
2384 	if (IS_APPEND(inode)) {
2385 		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
2386 			return -EPERM;
2387 		if (flag & O_TRUNC)
2388 			return -EPERM;
2389 	}
2390 
2391 	/* O_NOATIME can only be set by the owner or superuser */
2392 	if (flag & O_NOATIME && !inode_owner_or_capable(inode))
2393 		return -EPERM;
2394 
2395 	return 0;
2396 }
2397 
2398 static int handle_truncate(struct file *filp)
2399 {
2400 	struct path *path = &filp->f_path;
2401 	struct inode *inode = path->dentry->d_inode;
2402 	int error = get_write_access(inode);
2403 	if (error)
2404 		return error;
2405 	/*
2406 	 * Refuse to truncate files with mandatory locks held on them.
2407 	 */
2408 	error = locks_verify_locked(inode);
2409 	if (!error)
2410 		error = security_path_truncate(path);
2411 	if (!error) {
2412 		error = do_truncate(path->dentry, 0,
2413 				    ATTR_MTIME|ATTR_CTIME|ATTR_OPEN,
2414 				    filp);
2415 	}
2416 	put_write_access(inode);
2417 	return error;
2418 }
2419 
2420 static inline int open_to_namei_flags(int flag)
2421 {
2422 	if ((flag & O_ACCMODE) == 3)
2423 		flag--;
2424 	return flag;
2425 }
2426 
2427 static int may_o_create(struct path *dir, struct dentry *dentry, umode_t mode)
2428 {
2429 	int error = security_path_mknod(dir, dentry, mode, 0);
2430 	if (error)
2431 		return error;
2432 
2433 	error = inode_permission(dir->dentry->d_inode, MAY_WRITE | MAY_EXEC);
2434 	if (error)
2435 		return error;
2436 
2437 	return security_inode_create(dir->dentry->d_inode, dentry, mode);
2438 }
2439 
2440 /*
2441  * Attempt to atomically look up, create and open a file from a negative
2442  * dentry.
2443  *
2444  * Returns 0 if successful.  The file will have been created and attached to
2445  * @file by the filesystem calling finish_open().
2446  *
2447  * Returns 1 if the file was looked up only or didn't need creating.  The
2448  * caller will need to perform the open themselves.  @path will have been
2449  * updated to point to the new dentry.  This may be negative.
2450  *
2451  * Returns an error code otherwise.
2452  */
2453 static int atomic_open(struct nameidata *nd, struct dentry *dentry,
2454 			struct path *path, struct file *file,
2455 			const struct open_flags *op,
2456 			bool got_write, bool need_lookup,
2457 			int *opened)
2458 {
2459 	struct inode *dir =  nd->path.dentry->d_inode;
2460 	unsigned open_flag = open_to_namei_flags(op->open_flag);
2461 	umode_t mode;
2462 	int error;
2463 	int acc_mode;
2464 	int create_error = 0;
2465 	struct dentry *const DENTRY_NOT_SET = (void *) -1UL;
2466 
2467 	BUG_ON(dentry->d_inode);
2468 
2469 	/* Don't create child dentry for a dead directory. */
2470 	if (unlikely(IS_DEADDIR(dir))) {
2471 		error = -ENOENT;
2472 		goto out;
2473 	}
2474 
2475 	mode = op->mode;
2476 	if ((open_flag & O_CREAT) && !IS_POSIXACL(dir))
2477 		mode &= ~current_umask();
2478 
2479 	if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT)) {
2480 		open_flag &= ~O_TRUNC;
2481 		*opened |= FILE_CREATED;
2482 	}
2483 
2484 	/*
2485 	 * Checking write permission is tricky, bacuse we don't know if we are
2486 	 * going to actually need it: O_CREAT opens should work as long as the
2487 	 * file exists.  But checking existence breaks atomicity.  The trick is
2488 	 * to check access and if not granted clear O_CREAT from the flags.
2489 	 *
2490 	 * Another problem is returing the "right" error value (e.g. for an
2491 	 * O_EXCL open we want to return EEXIST not EROFS).
2492 	 */
2493 	if (((open_flag & (O_CREAT | O_TRUNC)) ||
2494 	    (open_flag & O_ACCMODE) != O_RDONLY) && unlikely(!got_write)) {
2495 		if (!(open_flag & O_CREAT)) {
2496 			/*
2497 			 * No O_CREATE -> atomicity not a requirement -> fall
2498 			 * back to lookup + open
2499 			 */
2500 			goto no_open;
2501 		} else if (open_flag & (O_EXCL | O_TRUNC)) {
2502 			/* Fall back and fail with the right error */
2503 			create_error = -EROFS;
2504 			goto no_open;
2505 		} else {
2506 			/* No side effects, safe to clear O_CREAT */
2507 			create_error = -EROFS;
2508 			open_flag &= ~O_CREAT;
2509 		}
2510 	}
2511 
2512 	if (open_flag & O_CREAT) {
2513 		error = may_o_create(&nd->path, dentry, mode);
2514 		if (error) {
2515 			create_error = error;
2516 			if (open_flag & O_EXCL)
2517 				goto no_open;
2518 			open_flag &= ~O_CREAT;
2519 		}
2520 	}
2521 
2522 	if (nd->flags & LOOKUP_DIRECTORY)
2523 		open_flag |= O_DIRECTORY;
2524 
2525 	file->f_path.dentry = DENTRY_NOT_SET;
2526 	file->f_path.mnt = nd->path.mnt;
2527 	error = dir->i_op->atomic_open(dir, dentry, file, open_flag, mode,
2528 				      opened);
2529 	if (error < 0) {
2530 		if (create_error && error == -ENOENT)
2531 			error = create_error;
2532 		goto out;
2533 	}
2534 
2535 	acc_mode = op->acc_mode;
2536 	if (*opened & FILE_CREATED) {
2537 		fsnotify_create(dir, dentry);
2538 		acc_mode = MAY_OPEN;
2539 	}
2540 
2541 	if (error) {	/* returned 1, that is */
2542 		if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
2543 			error = -EIO;
2544 			goto out;
2545 		}
2546 		if (file->f_path.dentry) {
2547 			dput(dentry);
2548 			dentry = file->f_path.dentry;
2549 		}
2550 		if (create_error && dentry->d_inode == NULL) {
2551 			error = create_error;
2552 			goto out;
2553 		}
2554 		goto looked_up;
2555 	}
2556 
2557 	/*
2558 	 * We didn't have the inode before the open, so check open permission
2559 	 * here.
2560 	 */
2561 	error = may_open(&file->f_path, acc_mode, open_flag);
2562 	if (error)
2563 		fput(file);
2564 
2565 out:
2566 	dput(dentry);
2567 	return error;
2568 
2569 no_open:
2570 	if (need_lookup) {
2571 		dentry = lookup_real(dir, dentry, nd->flags);
2572 		if (IS_ERR(dentry))
2573 			return PTR_ERR(dentry);
2574 
2575 		if (create_error) {
2576 			int open_flag = op->open_flag;
2577 
2578 			error = create_error;
2579 			if ((open_flag & O_EXCL)) {
2580 				if (!dentry->d_inode)
2581 					goto out;
2582 			} else if (!dentry->d_inode) {
2583 				goto out;
2584 			} else if ((open_flag & O_TRUNC) &&
2585 				   S_ISREG(dentry->d_inode->i_mode)) {
2586 				goto out;
2587 			}
2588 			/* will fail later, go on to get the right error */
2589 		}
2590 	}
2591 looked_up:
2592 	path->dentry = dentry;
2593 	path->mnt = nd->path.mnt;
2594 	return 1;
2595 }
2596 
2597 /*
2598  * Look up and maybe create and open the last component.
2599  *
2600  * Must be called with i_mutex held on parent.
2601  *
2602  * Returns 0 if the file was successfully atomically created (if necessary) and
2603  * opened.  In this case the file will be returned attached to @file.
2604  *
2605  * Returns 1 if the file was not completely opened at this time, though lookups
2606  * and creations will have been performed and the dentry returned in @path will
2607  * be positive upon return if O_CREAT was specified.  If O_CREAT wasn't
2608  * specified then a negative dentry may be returned.
2609  *
2610  * An error code is returned otherwise.
2611  *
2612  * FILE_CREATE will be set in @*opened if the dentry was created and will be
2613  * cleared otherwise prior to returning.
2614  */
2615 static int lookup_open(struct nameidata *nd, struct path *path,
2616 			struct file *file,
2617 			const struct open_flags *op,
2618 			bool got_write, int *opened)
2619 {
2620 	struct dentry *dir = nd->path.dentry;
2621 	struct inode *dir_inode = dir->d_inode;
2622 	struct dentry *dentry;
2623 	int error;
2624 	bool need_lookup;
2625 
2626 	*opened &= ~FILE_CREATED;
2627 	dentry = lookup_dcache(&nd->last, dir, nd->flags, &need_lookup);
2628 	if (IS_ERR(dentry))
2629 		return PTR_ERR(dentry);
2630 
2631 	/* Cached positive dentry: will open in f_op->open */
2632 	if (!need_lookup && dentry->d_inode)
2633 		goto out_no_open;
2634 
2635 	if ((nd->flags & LOOKUP_OPEN) && dir_inode->i_op->atomic_open) {
2636 		return atomic_open(nd, dentry, path, file, op, got_write,
2637 				   need_lookup, opened);
2638 	}
2639 
2640 	if (need_lookup) {
2641 		BUG_ON(dentry->d_inode);
2642 
2643 		dentry = lookup_real(dir_inode, dentry, nd->flags);
2644 		if (IS_ERR(dentry))
2645 			return PTR_ERR(dentry);
2646 	}
2647 
2648 	/* Negative dentry, just create the file */
2649 	if (!dentry->d_inode && (op->open_flag & O_CREAT)) {
2650 		umode_t mode = op->mode;
2651 		if (!IS_POSIXACL(dir->d_inode))
2652 			mode &= ~current_umask();
2653 		/*
2654 		 * This write is needed to ensure that a
2655 		 * rw->ro transition does not occur between
2656 		 * the time when the file is created and when
2657 		 * a permanent write count is taken through
2658 		 * the 'struct file' in finish_open().
2659 		 */
2660 		if (!got_write) {
2661 			error = -EROFS;
2662 			goto out_dput;
2663 		}
2664 		*opened |= FILE_CREATED;
2665 		error = security_path_mknod(&nd->path, dentry, mode, 0);
2666 		if (error)
2667 			goto out_dput;
2668 		error = vfs_create(dir->d_inode, dentry, mode,
2669 				   nd->flags & LOOKUP_EXCL);
2670 		if (error)
2671 			goto out_dput;
2672 	}
2673 out_no_open:
2674 	path->dentry = dentry;
2675 	path->mnt = nd->path.mnt;
2676 	return 1;
2677 
2678 out_dput:
2679 	dput(dentry);
2680 	return error;
2681 }
2682 
2683 /*
2684  * Handle the last step of open()
2685  */
2686 static int do_last(struct nameidata *nd, struct path *path,
2687 		   struct file *file, const struct open_flags *op,
2688 		   int *opened, struct filename *name)
2689 {
2690 	struct dentry *dir = nd->path.dentry;
2691 	int open_flag = op->open_flag;
2692 	bool will_truncate = (open_flag & O_TRUNC) != 0;
2693 	bool got_write = false;
2694 	int acc_mode = op->acc_mode;
2695 	struct inode *inode;
2696 	bool symlink_ok = false;
2697 	struct path save_parent = { .dentry = NULL, .mnt = NULL };
2698 	bool retried = false;
2699 	int error;
2700 
2701 	nd->flags &= ~LOOKUP_PARENT;
2702 	nd->flags |= op->intent;
2703 
2704 	switch (nd->last_type) {
2705 	case LAST_DOTDOT:
2706 	case LAST_DOT:
2707 		error = handle_dots(nd, nd->last_type);
2708 		if (error)
2709 			return error;
2710 		/* fallthrough */
2711 	case LAST_ROOT:
2712 		error = complete_walk(nd);
2713 		if (error)
2714 			return error;
2715 		audit_inode(name, nd->path.dentry, 0);
2716 		if (open_flag & O_CREAT) {
2717 			error = -EISDIR;
2718 			goto out;
2719 		}
2720 		goto finish_open;
2721 	case LAST_BIND:
2722 		error = complete_walk(nd);
2723 		if (error)
2724 			return error;
2725 		audit_inode(name, dir, 0);
2726 		goto finish_open;
2727 	}
2728 
2729 	if (!(open_flag & O_CREAT)) {
2730 		if (nd->last.name[nd->last.len])
2731 			nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
2732 		if (open_flag & O_PATH && !(nd->flags & LOOKUP_FOLLOW))
2733 			symlink_ok = true;
2734 		/* we _can_ be in RCU mode here */
2735 		error = lookup_fast(nd, &nd->last, path, &inode);
2736 		if (likely(!error))
2737 			goto finish_lookup;
2738 
2739 		if (error < 0)
2740 			goto out;
2741 
2742 		BUG_ON(nd->inode != dir->d_inode);
2743 	} else {
2744 		/* create side of things */
2745 		/*
2746 		 * This will *only* deal with leaving RCU mode - LOOKUP_JUMPED
2747 		 * has been cleared when we got to the last component we are
2748 		 * about to look up
2749 		 */
2750 		error = complete_walk(nd);
2751 		if (error)
2752 			return error;
2753 
2754 		audit_inode(name, dir, 0);
2755 		error = -EISDIR;
2756 		/* trailing slashes? */
2757 		if (nd->last.name[nd->last.len])
2758 			goto out;
2759 	}
2760 
2761 retry_lookup:
2762 	if (op->open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
2763 		error = mnt_want_write(nd->path.mnt);
2764 		if (!error)
2765 			got_write = true;
2766 		/*
2767 		 * do _not_ fail yet - we might not need that or fail with
2768 		 * a different error; let lookup_open() decide; we'll be
2769 		 * dropping this one anyway.
2770 		 */
2771 	}
2772 	mutex_lock(&dir->d_inode->i_mutex);
2773 	error = lookup_open(nd, path, file, op, got_write, opened);
2774 	mutex_unlock(&dir->d_inode->i_mutex);
2775 
2776 	if (error <= 0) {
2777 		if (error)
2778 			goto out;
2779 
2780 		if ((*opened & FILE_CREATED) ||
2781 		    !S_ISREG(file->f_path.dentry->d_inode->i_mode))
2782 			will_truncate = false;
2783 
2784 		audit_inode(name, file->f_path.dentry, 0);
2785 		goto opened;
2786 	}
2787 
2788 	if (*opened & FILE_CREATED) {
2789 		/* Don't check for write permission, don't truncate */
2790 		open_flag &= ~O_TRUNC;
2791 		will_truncate = false;
2792 		acc_mode = MAY_OPEN;
2793 		path_to_nameidata(path, nd);
2794 		goto finish_open_created;
2795 	}
2796 
2797 	/*
2798 	 * create/update audit record if it already exists.
2799 	 */
2800 	if (path->dentry->d_inode)
2801 		audit_inode(name, path->dentry, 0);
2802 
2803 	/*
2804 	 * If atomic_open() acquired write access it is dropped now due to
2805 	 * possible mount and symlink following (this might be optimized away if
2806 	 * necessary...)
2807 	 */
2808 	if (got_write) {
2809 		mnt_drop_write(nd->path.mnt);
2810 		got_write = false;
2811 	}
2812 
2813 	error = -EEXIST;
2814 	if ((open_flag & (O_EXCL | O_CREAT)) == (O_EXCL | O_CREAT))
2815 		goto exit_dput;
2816 
2817 	error = follow_managed(path, nd->flags);
2818 	if (error < 0)
2819 		goto exit_dput;
2820 
2821 	if (error)
2822 		nd->flags |= LOOKUP_JUMPED;
2823 
2824 	BUG_ON(nd->flags & LOOKUP_RCU);
2825 	inode = path->dentry->d_inode;
2826 finish_lookup:
2827 	/* we _can_ be in RCU mode here */
2828 	error = -ENOENT;
2829 	if (!inode) {
2830 		path_to_nameidata(path, nd);
2831 		goto out;
2832 	}
2833 
2834 	if (should_follow_link(inode, !symlink_ok)) {
2835 		if (nd->flags & LOOKUP_RCU) {
2836 			if (unlikely(unlazy_walk(nd, path->dentry))) {
2837 				error = -ECHILD;
2838 				goto out;
2839 			}
2840 		}
2841 		BUG_ON(inode != path->dentry->d_inode);
2842 		return 1;
2843 	}
2844 
2845 	if ((nd->flags & LOOKUP_RCU) || nd->path.mnt != path->mnt) {
2846 		path_to_nameidata(path, nd);
2847 	} else {
2848 		save_parent.dentry = nd->path.dentry;
2849 		save_parent.mnt = mntget(path->mnt);
2850 		nd->path.dentry = path->dentry;
2851 
2852 	}
2853 	nd->inode = inode;
2854 	/* Why this, you ask?  _Now_ we might have grown LOOKUP_JUMPED... */
2855 	error = complete_walk(nd);
2856 	if (error) {
2857 		path_put(&save_parent);
2858 		return error;
2859 	}
2860 	error = -EISDIR;
2861 	if ((open_flag & O_CREAT) && S_ISDIR(nd->inode->i_mode))
2862 		goto out;
2863 	error = -ENOTDIR;
2864 	if ((nd->flags & LOOKUP_DIRECTORY) && !nd->inode->i_op->lookup)
2865 		goto out;
2866 	audit_inode(name, nd->path.dentry, 0);
2867 finish_open:
2868 	if (!S_ISREG(nd->inode->i_mode))
2869 		will_truncate = false;
2870 
2871 	if (will_truncate) {
2872 		error = mnt_want_write(nd->path.mnt);
2873 		if (error)
2874 			goto out;
2875 		got_write = true;
2876 	}
2877 finish_open_created:
2878 	error = may_open(&nd->path, acc_mode, open_flag);
2879 	if (error)
2880 		goto out;
2881 	file->f_path.mnt = nd->path.mnt;
2882 	error = finish_open(file, nd->path.dentry, NULL, opened);
2883 	if (error) {
2884 		if (error == -EOPENSTALE)
2885 			goto stale_open;
2886 		goto out;
2887 	}
2888 opened:
2889 	error = open_check_o_direct(file);
2890 	if (error)
2891 		goto exit_fput;
2892 	error = ima_file_check(file, op->acc_mode);
2893 	if (error)
2894 		goto exit_fput;
2895 
2896 	if (will_truncate) {
2897 		error = handle_truncate(file);
2898 		if (error)
2899 			goto exit_fput;
2900 	}
2901 out:
2902 	if (got_write)
2903 		mnt_drop_write(nd->path.mnt);
2904 	path_put(&save_parent);
2905 	terminate_walk(nd);
2906 	return error;
2907 
2908 exit_dput:
2909 	path_put_conditional(path, nd);
2910 	goto out;
2911 exit_fput:
2912 	fput(file);
2913 	goto out;
2914 
2915 stale_open:
2916 	/* If no saved parent or already retried then can't retry */
2917 	if (!save_parent.dentry || retried)
2918 		goto out;
2919 
2920 	BUG_ON(save_parent.dentry != dir);
2921 	path_put(&nd->path);
2922 	nd->path = save_parent;
2923 	nd->inode = dir->d_inode;
2924 	save_parent.mnt = NULL;
2925 	save_parent.dentry = NULL;
2926 	if (got_write) {
2927 		mnt_drop_write(nd->path.mnt);
2928 		got_write = false;
2929 	}
2930 	retried = true;
2931 	goto retry_lookup;
2932 }
2933 
2934 static struct file *path_openat(int dfd, struct filename *pathname,
2935 		struct nameidata *nd, const struct open_flags *op, int flags)
2936 {
2937 	struct file *base = NULL;
2938 	struct file *file;
2939 	struct path path;
2940 	int opened = 0;
2941 	int error;
2942 
2943 	file = get_empty_filp();
2944 	if (!file)
2945 		return ERR_PTR(-ENFILE);
2946 
2947 	file->f_flags = op->open_flag;
2948 
2949 	error = path_init(dfd, pathname->name, flags | LOOKUP_PARENT, nd, &base);
2950 	if (unlikely(error))
2951 		goto out;
2952 
2953 	current->total_link_count = 0;
2954 	error = link_path_walk(pathname->name, nd);
2955 	if (unlikely(error))
2956 		goto out;
2957 
2958 	error = do_last(nd, &path, file, op, &opened, pathname);
2959 	while (unlikely(error > 0)) { /* trailing symlink */
2960 		struct path link = path;
2961 		void *cookie;
2962 		if (!(nd->flags & LOOKUP_FOLLOW)) {
2963 			path_put_conditional(&path, nd);
2964 			path_put(&nd->path);
2965 			error = -ELOOP;
2966 			break;
2967 		}
2968 		error = may_follow_link(&link, nd);
2969 		if (unlikely(error))
2970 			break;
2971 		nd->flags |= LOOKUP_PARENT;
2972 		nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL);
2973 		error = follow_link(&link, nd, &cookie);
2974 		if (unlikely(error))
2975 			break;
2976 		error = do_last(nd, &path, file, op, &opened, pathname);
2977 		put_link(nd, &link, cookie);
2978 	}
2979 out:
2980 	if (nd->root.mnt && !(nd->flags & LOOKUP_ROOT))
2981 		path_put(&nd->root);
2982 	if (base)
2983 		fput(base);
2984 	if (!(opened & FILE_OPENED)) {
2985 		BUG_ON(!error);
2986 		put_filp(file);
2987 	}
2988 	if (unlikely(error)) {
2989 		if (error == -EOPENSTALE) {
2990 			if (flags & LOOKUP_RCU)
2991 				error = -ECHILD;
2992 			else
2993 				error = -ESTALE;
2994 		}
2995 		file = ERR_PTR(error);
2996 	}
2997 	return file;
2998 }
2999 
3000 struct file *do_filp_open(int dfd, struct filename *pathname,
3001 		const struct open_flags *op, int flags)
3002 {
3003 	struct nameidata nd;
3004 	struct file *filp;
3005 
3006 	filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_RCU);
3007 	if (unlikely(filp == ERR_PTR(-ECHILD)))
3008 		filp = path_openat(dfd, pathname, &nd, op, flags);
3009 	if (unlikely(filp == ERR_PTR(-ESTALE)))
3010 		filp = path_openat(dfd, pathname, &nd, op, flags | LOOKUP_REVAL);
3011 	return filp;
3012 }
3013 
3014 struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
3015 		const char *name, const struct open_flags *op, int flags)
3016 {
3017 	struct nameidata nd;
3018 	struct file *file;
3019 	struct filename filename = { .name = name };
3020 
3021 	nd.root.mnt = mnt;
3022 	nd.root.dentry = dentry;
3023 
3024 	flags |= LOOKUP_ROOT;
3025 
3026 	if (dentry->d_inode->i_op->follow_link && op->intent & LOOKUP_OPEN)
3027 		return ERR_PTR(-ELOOP);
3028 
3029 	file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_RCU);
3030 	if (unlikely(file == ERR_PTR(-ECHILD)))
3031 		file = path_openat(-1, &filename, &nd, op, flags);
3032 	if (unlikely(file == ERR_PTR(-ESTALE)))
3033 		file = path_openat(-1, &filename, &nd, op, flags | LOOKUP_REVAL);
3034 	return file;
3035 }
3036 
3037 struct dentry *kern_path_create(int dfd, const char *pathname,
3038 				struct path *path, unsigned int lookup_flags)
3039 {
3040 	struct dentry *dentry = ERR_PTR(-EEXIST);
3041 	struct nameidata nd;
3042 	int err2;
3043 	int error;
3044 	bool is_dir = (lookup_flags & LOOKUP_DIRECTORY);
3045 
3046 	/*
3047 	 * Note that only LOOKUP_REVAL and LOOKUP_DIRECTORY matter here. Any
3048 	 * other flags passed in are ignored!
3049 	 */
3050 	lookup_flags &= LOOKUP_REVAL;
3051 
3052 	error = do_path_lookup(dfd, pathname, LOOKUP_PARENT|lookup_flags, &nd);
3053 	if (error)
3054 		return ERR_PTR(error);
3055 
3056 	/*
3057 	 * Yucky last component or no last component at all?
3058 	 * (foo/., foo/.., /////)
3059 	 */
3060 	if (nd.last_type != LAST_NORM)
3061 		goto out;
3062 	nd.flags &= ~LOOKUP_PARENT;
3063 	nd.flags |= LOOKUP_CREATE | LOOKUP_EXCL;
3064 
3065 	/* don't fail immediately if it's r/o, at least try to report other errors */
3066 	err2 = mnt_want_write(nd.path.mnt);
3067 	/*
3068 	 * Do the final lookup.
3069 	 */
3070 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3071 	dentry = lookup_hash(&nd);
3072 	if (IS_ERR(dentry))
3073 		goto unlock;
3074 
3075 	error = -EEXIST;
3076 	if (dentry->d_inode)
3077 		goto fail;
3078 	/*
3079 	 * Special case - lookup gave negative, but... we had foo/bar/
3080 	 * From the vfs_mknod() POV we just have a negative dentry -
3081 	 * all is fine. Let's be bastards - you had / on the end, you've
3082 	 * been asking for (non-existent) directory. -ENOENT for you.
3083 	 */
3084 	if (unlikely(!is_dir && nd.last.name[nd.last.len])) {
3085 		error = -ENOENT;
3086 		goto fail;
3087 	}
3088 	if (unlikely(err2)) {
3089 		error = err2;
3090 		goto fail;
3091 	}
3092 	*path = nd.path;
3093 	return dentry;
3094 fail:
3095 	dput(dentry);
3096 	dentry = ERR_PTR(error);
3097 unlock:
3098 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3099 	if (!err2)
3100 		mnt_drop_write(nd.path.mnt);
3101 out:
3102 	path_put(&nd.path);
3103 	return dentry;
3104 }
3105 EXPORT_SYMBOL(kern_path_create);
3106 
3107 void done_path_create(struct path *path, struct dentry *dentry)
3108 {
3109 	dput(dentry);
3110 	mutex_unlock(&path->dentry->d_inode->i_mutex);
3111 	mnt_drop_write(path->mnt);
3112 	path_put(path);
3113 }
3114 EXPORT_SYMBOL(done_path_create);
3115 
3116 struct dentry *user_path_create(int dfd, const char __user *pathname,
3117 				struct path *path, unsigned int lookup_flags)
3118 {
3119 	struct filename *tmp = getname(pathname);
3120 	struct dentry *res;
3121 	if (IS_ERR(tmp))
3122 		return ERR_CAST(tmp);
3123 	res = kern_path_create(dfd, tmp->name, path, lookup_flags);
3124 	putname(tmp);
3125 	return res;
3126 }
3127 EXPORT_SYMBOL(user_path_create);
3128 
3129 int vfs_mknod(struct inode *dir, struct dentry *dentry, umode_t mode, dev_t dev)
3130 {
3131 	int error = may_create(dir, dentry);
3132 
3133 	if (error)
3134 		return error;
3135 
3136 	if ((S_ISCHR(mode) || S_ISBLK(mode)) && !capable(CAP_MKNOD))
3137 		return -EPERM;
3138 
3139 	if (!dir->i_op->mknod)
3140 		return -EPERM;
3141 
3142 	error = devcgroup_inode_mknod(mode, dev);
3143 	if (error)
3144 		return error;
3145 
3146 	error = security_inode_mknod(dir, dentry, mode, dev);
3147 	if (error)
3148 		return error;
3149 
3150 	error = dir->i_op->mknod(dir, dentry, mode, dev);
3151 	if (!error)
3152 		fsnotify_create(dir, dentry);
3153 	return error;
3154 }
3155 
3156 static int may_mknod(umode_t mode)
3157 {
3158 	switch (mode & S_IFMT) {
3159 	case S_IFREG:
3160 	case S_IFCHR:
3161 	case S_IFBLK:
3162 	case S_IFIFO:
3163 	case S_IFSOCK:
3164 	case 0: /* zero mode translates to S_IFREG */
3165 		return 0;
3166 	case S_IFDIR:
3167 		return -EPERM;
3168 	default:
3169 		return -EINVAL;
3170 	}
3171 }
3172 
3173 SYSCALL_DEFINE4(mknodat, int, dfd, const char __user *, filename, umode_t, mode,
3174 		unsigned, dev)
3175 {
3176 	struct dentry *dentry;
3177 	struct path path;
3178 	int error;
3179 	unsigned int lookup_flags = 0;
3180 
3181 	error = may_mknod(mode);
3182 	if (error)
3183 		return error;
3184 retry:
3185 	dentry = user_path_create(dfd, filename, &path, lookup_flags);
3186 	if (IS_ERR(dentry))
3187 		return PTR_ERR(dentry);
3188 
3189 	if (!IS_POSIXACL(path.dentry->d_inode))
3190 		mode &= ~current_umask();
3191 	error = security_path_mknod(&path, dentry, mode, dev);
3192 	if (error)
3193 		goto out;
3194 	switch (mode & S_IFMT) {
3195 		case 0: case S_IFREG:
3196 			error = vfs_create(path.dentry->d_inode,dentry,mode,true);
3197 			break;
3198 		case S_IFCHR: case S_IFBLK:
3199 			error = vfs_mknod(path.dentry->d_inode,dentry,mode,
3200 					new_decode_dev(dev));
3201 			break;
3202 		case S_IFIFO: case S_IFSOCK:
3203 			error = vfs_mknod(path.dentry->d_inode,dentry,mode,0);
3204 			break;
3205 	}
3206 out:
3207 	done_path_create(&path, dentry);
3208 	if (retry_estale(error, lookup_flags)) {
3209 		lookup_flags |= LOOKUP_REVAL;
3210 		goto retry;
3211 	}
3212 	return error;
3213 }
3214 
3215 SYSCALL_DEFINE3(mknod, const char __user *, filename, umode_t, mode, unsigned, dev)
3216 {
3217 	return sys_mknodat(AT_FDCWD, filename, mode, dev);
3218 }
3219 
3220 int vfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
3221 {
3222 	int error = may_create(dir, dentry);
3223 	unsigned max_links = dir->i_sb->s_max_links;
3224 
3225 	if (error)
3226 		return error;
3227 
3228 	if (!dir->i_op->mkdir)
3229 		return -EPERM;
3230 
3231 	mode &= (S_IRWXUGO|S_ISVTX);
3232 	error = security_inode_mkdir(dir, dentry, mode);
3233 	if (error)
3234 		return error;
3235 
3236 	if (max_links && dir->i_nlink >= max_links)
3237 		return -EMLINK;
3238 
3239 	error = dir->i_op->mkdir(dir, dentry, mode);
3240 	if (!error)
3241 		fsnotify_mkdir(dir, dentry);
3242 	return error;
3243 }
3244 
3245 SYSCALL_DEFINE3(mkdirat, int, dfd, const char __user *, pathname, umode_t, mode)
3246 {
3247 	struct dentry *dentry;
3248 	struct path path;
3249 	int error;
3250 	unsigned int lookup_flags = LOOKUP_DIRECTORY;
3251 
3252 retry:
3253 	dentry = user_path_create(dfd, pathname, &path, lookup_flags);
3254 	if (IS_ERR(dentry))
3255 		return PTR_ERR(dentry);
3256 
3257 	if (!IS_POSIXACL(path.dentry->d_inode))
3258 		mode &= ~current_umask();
3259 	error = security_path_mkdir(&path, dentry, mode);
3260 	if (!error)
3261 		error = vfs_mkdir(path.dentry->d_inode, dentry, mode);
3262 	done_path_create(&path, dentry);
3263 	if (retry_estale(error, lookup_flags)) {
3264 		lookup_flags |= LOOKUP_REVAL;
3265 		goto retry;
3266 	}
3267 	return error;
3268 }
3269 
3270 SYSCALL_DEFINE2(mkdir, const char __user *, pathname, umode_t, mode)
3271 {
3272 	return sys_mkdirat(AT_FDCWD, pathname, mode);
3273 }
3274 
3275 /*
3276  * The dentry_unhash() helper will try to drop the dentry early: we
3277  * should have a usage count of 1 if we're the only user of this
3278  * dentry, and if that is true (possibly after pruning the dcache),
3279  * then we drop the dentry now.
3280  *
3281  * A low-level filesystem can, if it choses, legally
3282  * do a
3283  *
3284  *	if (!d_unhashed(dentry))
3285  *		return -EBUSY;
3286  *
3287  * if it cannot handle the case of removing a directory
3288  * that is still in use by something else..
3289  */
3290 void dentry_unhash(struct dentry *dentry)
3291 {
3292 	shrink_dcache_parent(dentry);
3293 	spin_lock(&dentry->d_lock);
3294 	if (dentry->d_count == 1)
3295 		__d_drop(dentry);
3296 	spin_unlock(&dentry->d_lock);
3297 }
3298 
3299 int vfs_rmdir(struct inode *dir, struct dentry *dentry)
3300 {
3301 	int error = may_delete(dir, dentry, 1);
3302 
3303 	if (error)
3304 		return error;
3305 
3306 	if (!dir->i_op->rmdir)
3307 		return -EPERM;
3308 
3309 	dget(dentry);
3310 	mutex_lock(&dentry->d_inode->i_mutex);
3311 
3312 	error = -EBUSY;
3313 	if (d_mountpoint(dentry))
3314 		goto out;
3315 
3316 	error = security_inode_rmdir(dir, dentry);
3317 	if (error)
3318 		goto out;
3319 
3320 	shrink_dcache_parent(dentry);
3321 	error = dir->i_op->rmdir(dir, dentry);
3322 	if (error)
3323 		goto out;
3324 
3325 	dentry->d_inode->i_flags |= S_DEAD;
3326 	dont_mount(dentry);
3327 
3328 out:
3329 	mutex_unlock(&dentry->d_inode->i_mutex);
3330 	dput(dentry);
3331 	if (!error)
3332 		d_delete(dentry);
3333 	return error;
3334 }
3335 
3336 static long do_rmdir(int dfd, const char __user *pathname)
3337 {
3338 	int error = 0;
3339 	struct filename *name;
3340 	struct dentry *dentry;
3341 	struct nameidata nd;
3342 	unsigned int lookup_flags = 0;
3343 retry:
3344 	name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3345 	if (IS_ERR(name))
3346 		return PTR_ERR(name);
3347 
3348 	switch(nd.last_type) {
3349 	case LAST_DOTDOT:
3350 		error = -ENOTEMPTY;
3351 		goto exit1;
3352 	case LAST_DOT:
3353 		error = -EINVAL;
3354 		goto exit1;
3355 	case LAST_ROOT:
3356 		error = -EBUSY;
3357 		goto exit1;
3358 	}
3359 
3360 	nd.flags &= ~LOOKUP_PARENT;
3361 	error = mnt_want_write(nd.path.mnt);
3362 	if (error)
3363 		goto exit1;
3364 
3365 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3366 	dentry = lookup_hash(&nd);
3367 	error = PTR_ERR(dentry);
3368 	if (IS_ERR(dentry))
3369 		goto exit2;
3370 	if (!dentry->d_inode) {
3371 		error = -ENOENT;
3372 		goto exit3;
3373 	}
3374 	error = security_path_rmdir(&nd.path, dentry);
3375 	if (error)
3376 		goto exit3;
3377 	error = vfs_rmdir(nd.path.dentry->d_inode, dentry);
3378 exit3:
3379 	dput(dentry);
3380 exit2:
3381 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3382 	mnt_drop_write(nd.path.mnt);
3383 exit1:
3384 	path_put(&nd.path);
3385 	putname(name);
3386 	if (retry_estale(error, lookup_flags)) {
3387 		lookup_flags |= LOOKUP_REVAL;
3388 		goto retry;
3389 	}
3390 	return error;
3391 }
3392 
3393 SYSCALL_DEFINE1(rmdir, const char __user *, pathname)
3394 {
3395 	return do_rmdir(AT_FDCWD, pathname);
3396 }
3397 
3398 int vfs_unlink(struct inode *dir, struct dentry *dentry)
3399 {
3400 	int error = may_delete(dir, dentry, 0);
3401 
3402 	if (error)
3403 		return error;
3404 
3405 	if (!dir->i_op->unlink)
3406 		return -EPERM;
3407 
3408 	mutex_lock(&dentry->d_inode->i_mutex);
3409 	if (d_mountpoint(dentry))
3410 		error = -EBUSY;
3411 	else {
3412 		error = security_inode_unlink(dir, dentry);
3413 		if (!error) {
3414 			error = dir->i_op->unlink(dir, dentry);
3415 			if (!error)
3416 				dont_mount(dentry);
3417 		}
3418 	}
3419 	mutex_unlock(&dentry->d_inode->i_mutex);
3420 
3421 	/* We don't d_delete() NFS sillyrenamed files--they still exist. */
3422 	if (!error && !(dentry->d_flags & DCACHE_NFSFS_RENAMED)) {
3423 		fsnotify_link_count(dentry->d_inode);
3424 		d_delete(dentry);
3425 	}
3426 
3427 	return error;
3428 }
3429 
3430 /*
3431  * Make sure that the actual truncation of the file will occur outside its
3432  * directory's i_mutex.  Truncate can take a long time if there is a lot of
3433  * writeout happening, and we don't want to prevent access to the directory
3434  * while waiting on the I/O.
3435  */
3436 static long do_unlinkat(int dfd, const char __user *pathname)
3437 {
3438 	int error;
3439 	struct filename *name;
3440 	struct dentry *dentry;
3441 	struct nameidata nd;
3442 	struct inode *inode = NULL;
3443 	unsigned int lookup_flags = 0;
3444 retry:
3445 	name = user_path_parent(dfd, pathname, &nd, lookup_flags);
3446 	if (IS_ERR(name))
3447 		return PTR_ERR(name);
3448 
3449 	error = -EISDIR;
3450 	if (nd.last_type != LAST_NORM)
3451 		goto exit1;
3452 
3453 	nd.flags &= ~LOOKUP_PARENT;
3454 	error = mnt_want_write(nd.path.mnt);
3455 	if (error)
3456 		goto exit1;
3457 
3458 	mutex_lock_nested(&nd.path.dentry->d_inode->i_mutex, I_MUTEX_PARENT);
3459 	dentry = lookup_hash(&nd);
3460 	error = PTR_ERR(dentry);
3461 	if (!IS_ERR(dentry)) {
3462 		/* Why not before? Because we want correct error value */
3463 		if (nd.last.name[nd.last.len])
3464 			goto slashes;
3465 		inode = dentry->d_inode;
3466 		if (!inode)
3467 			goto slashes;
3468 		ihold(inode);
3469 		error = security_path_unlink(&nd.path, dentry);
3470 		if (error)
3471 			goto exit2;
3472 		error = vfs_unlink(nd.path.dentry->d_inode, dentry);
3473 exit2:
3474 		dput(dentry);
3475 	}
3476 	mutex_unlock(&nd.path.dentry->d_inode->i_mutex);
3477 	if (inode)
3478 		iput(inode);	/* truncate the inode here */
3479 	mnt_drop_write(nd.path.mnt);
3480 exit1:
3481 	path_put(&nd.path);
3482 	putname(name);
3483 	if (retry_estale(error, lookup_flags)) {
3484 		lookup_flags |= LOOKUP_REVAL;
3485 		inode = NULL;
3486 		goto retry;
3487 	}
3488 	return error;
3489 
3490 slashes:
3491 	error = !dentry->d_inode ? -ENOENT :
3492 		S_ISDIR(dentry->d_inode->i_mode) ? -EISDIR : -ENOTDIR;
3493 	goto exit2;
3494 }
3495 
3496 SYSCALL_DEFINE3(unlinkat, int, dfd, const char __user *, pathname, int, flag)
3497 {
3498 	if ((flag & ~AT_REMOVEDIR) != 0)
3499 		return -EINVAL;
3500 
3501 	if (flag & AT_REMOVEDIR)
3502 		return do_rmdir(dfd, pathname);
3503 
3504 	return do_unlinkat(dfd, pathname);
3505 }
3506 
3507 SYSCALL_DEFINE1(unlink, const char __user *, pathname)
3508 {
3509 	return do_unlinkat(AT_FDCWD, pathname);
3510 }
3511 
3512 int vfs_symlink(struct inode *dir, struct dentry *dentry, const char *oldname)
3513 {
3514 	int error = may_create(dir, dentry);
3515 
3516 	if (error)
3517 		return error;
3518 
3519 	if (!dir->i_op->symlink)
3520 		return -EPERM;
3521 
3522 	error = security_inode_symlink(dir, dentry, oldname);
3523 	if (error)
3524 		return error;
3525 
3526 	error = dir->i_op->symlink(dir, dentry, oldname);
3527 	if (!error)
3528 		fsnotify_create(dir, dentry);
3529 	return error;
3530 }
3531 
3532 SYSCALL_DEFINE3(symlinkat, const char __user *, oldname,
3533 		int, newdfd, const char __user *, newname)
3534 {
3535 	int error;
3536 	struct filename *from;
3537 	struct dentry *dentry;
3538 	struct path path;
3539 	unsigned int lookup_flags = 0;
3540 
3541 	from = getname(oldname);
3542 	if (IS_ERR(from))
3543 		return PTR_ERR(from);
3544 retry:
3545 	dentry = user_path_create(newdfd, newname, &path, lookup_flags);
3546 	error = PTR_ERR(dentry);
3547 	if (IS_ERR(dentry))
3548 		goto out_putname;
3549 
3550 	error = security_path_symlink(&path, dentry, from->name);
3551 	if (!error)
3552 		error = vfs_symlink(path.dentry->d_inode, dentry, from->name);
3553 	done_path_create(&path, dentry);
3554 	if (retry_estale(error, lookup_flags)) {
3555 		lookup_flags |= LOOKUP_REVAL;
3556 		goto retry;
3557 	}
3558 out_putname:
3559 	putname(from);
3560 	return error;
3561 }
3562 
3563 SYSCALL_DEFINE2(symlink, const char __user *, oldname, const char __user *, newname)
3564 {
3565 	return sys_symlinkat(oldname, AT_FDCWD, newname);
3566 }
3567 
3568 int vfs_link(struct dentry *old_dentry, struct inode *dir, struct dentry *new_dentry)
3569 {
3570 	struct inode *inode = old_dentry->d_inode;
3571 	unsigned max_links = dir->i_sb->s_max_links;
3572 	int error;
3573 
3574 	if (!inode)
3575 		return -ENOENT;
3576 
3577 	error = may_create(dir, new_dentry);
3578 	if (error)
3579 		return error;
3580 
3581 	if (dir->i_sb != inode->i_sb)
3582 		return -EXDEV;
3583 
3584 	/*
3585 	 * A link to an append-only or immutable file cannot be created.
3586 	 */
3587 	if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
3588 		return -EPERM;
3589 	if (!dir->i_op->link)
3590 		return -EPERM;
3591 	if (S_ISDIR(inode->i_mode))
3592 		return -EPERM;
3593 
3594 	error = security_inode_link(old_dentry, dir, new_dentry);
3595 	if (error)
3596 		return error;
3597 
3598 	mutex_lock(&inode->i_mutex);
3599 	/* Make sure we don't allow creating hardlink to an unlinked file */
3600 	if (inode->i_nlink == 0)
3601 		error =  -ENOENT;
3602 	else if (max_links && inode->i_nlink >= max_links)
3603 		error = -EMLINK;
3604 	else
3605 		error = dir->i_op->link(old_dentry, dir, new_dentry);
3606 	mutex_unlock(&inode->i_mutex);
3607 	if (!error)
3608 		fsnotify_link(dir, inode, new_dentry);
3609 	return error;
3610 }
3611 
3612 /*
3613  * Hardlinks are often used in delicate situations.  We avoid
3614  * security-related surprises by not following symlinks on the
3615  * newname.  --KAB
3616  *
3617  * We don't follow them on the oldname either to be compatible
3618  * with linux 2.0, and to avoid hard-linking to directories
3619  * and other special files.  --ADM
3620  */
3621 SYSCALL_DEFINE5(linkat, int, olddfd, const char __user *, oldname,
3622 		int, newdfd, const char __user *, newname, int, flags)
3623 {
3624 	struct dentry *new_dentry;
3625 	struct path old_path, new_path;
3626 	int how = 0;
3627 	int error;
3628 
3629 	if ((flags & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
3630 		return -EINVAL;
3631 	/*
3632 	 * To use null names we require CAP_DAC_READ_SEARCH
3633 	 * This ensures that not everyone will be able to create
3634 	 * handlink using the passed filedescriptor.
3635 	 */
3636 	if (flags & AT_EMPTY_PATH) {
3637 		if (!capable(CAP_DAC_READ_SEARCH))
3638 			return -ENOENT;
3639 		how = LOOKUP_EMPTY;
3640 	}
3641 
3642 	if (flags & AT_SYMLINK_FOLLOW)
3643 		how |= LOOKUP_FOLLOW;
3644 retry:
3645 	error = user_path_at(olddfd, oldname, how, &old_path);
3646 	if (error)
3647 		return error;
3648 
3649 	new_dentry = user_path_create(newdfd, newname, &new_path,
3650 					(how & LOOKUP_REVAL));
3651 	error = PTR_ERR(new_dentry);
3652 	if (IS_ERR(new_dentry))
3653 		goto out;
3654 
3655 	error = -EXDEV;
3656 	if (old_path.mnt != new_path.mnt)
3657 		goto out_dput;
3658 	error = may_linkat(&old_path);
3659 	if (unlikely(error))
3660 		goto out_dput;
3661 	error = security_path_link(old_path.dentry, &new_path, new_dentry);
3662 	if (error)
3663 		goto out_dput;
3664 	error = vfs_link(old_path.dentry, new_path.dentry->d_inode, new_dentry);
3665 out_dput:
3666 	done_path_create(&new_path, new_dentry);
3667 	if (retry_estale(error, how)) {
3668 		how |= LOOKUP_REVAL;
3669 		goto retry;
3670 	}
3671 out:
3672 	path_put(&old_path);
3673 
3674 	return error;
3675 }
3676 
3677 SYSCALL_DEFINE2(link, const char __user *, oldname, const char __user *, newname)
3678 {
3679 	return sys_linkat(AT_FDCWD, oldname, AT_FDCWD, newname, 0);
3680 }
3681 
3682 /*
3683  * The worst of all namespace operations - renaming directory. "Perverted"
3684  * doesn't even start to describe it. Somebody in UCB had a heck of a trip...
3685  * Problems:
3686  *	a) we can get into loop creation. Check is done in is_subdir().
3687  *	b) race potential - two innocent renames can create a loop together.
3688  *	   That's where 4.4 screws up. Current fix: serialization on
3689  *	   sb->s_vfs_rename_mutex. We might be more accurate, but that's another
3690  *	   story.
3691  *	c) we have to lock _three_ objects - parents and victim (if it exists).
3692  *	   And that - after we got ->i_mutex on parents (until then we don't know
3693  *	   whether the target exists).  Solution: try to be smart with locking
3694  *	   order for inodes.  We rely on the fact that tree topology may change
3695  *	   only under ->s_vfs_rename_mutex _and_ that parent of the object we
3696  *	   move will be locked.  Thus we can rank directories by the tree
3697  *	   (ancestors first) and rank all non-directories after them.
3698  *	   That works since everybody except rename does "lock parent, lookup,
3699  *	   lock child" and rename is under ->s_vfs_rename_mutex.
3700  *	   HOWEVER, it relies on the assumption that any object with ->lookup()
3701  *	   has no more than 1 dentry.  If "hybrid" objects will ever appear,
3702  *	   we'd better make sure that there's no link(2) for them.
3703  *	d) conversion from fhandle to dentry may come in the wrong moment - when
3704  *	   we are removing the target. Solution: we will have to grab ->i_mutex
3705  *	   in the fhandle_to_dentry code. [FIXME - current nfsfh.c relies on
3706  *	   ->i_mutex on parents, which works but leads to some truly excessive
3707  *	   locking].
3708  */
3709 static int vfs_rename_dir(struct inode *old_dir, struct dentry *old_dentry,
3710 			  struct inode *new_dir, struct dentry *new_dentry)
3711 {
3712 	int error = 0;
3713 	struct inode *target = new_dentry->d_inode;
3714 	unsigned max_links = new_dir->i_sb->s_max_links;
3715 
3716 	/*
3717 	 * If we are going to change the parent - check write permissions,
3718 	 * we'll need to flip '..'.
3719 	 */
3720 	if (new_dir != old_dir) {
3721 		error = inode_permission(old_dentry->d_inode, MAY_WRITE);
3722 		if (error)
3723 			return error;
3724 	}
3725 
3726 	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3727 	if (error)
3728 		return error;
3729 
3730 	dget(new_dentry);
3731 	if (target)
3732 		mutex_lock(&target->i_mutex);
3733 
3734 	error = -EBUSY;
3735 	if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
3736 		goto out;
3737 
3738 	error = -EMLINK;
3739 	if (max_links && !target && new_dir != old_dir &&
3740 	    new_dir->i_nlink >= max_links)
3741 		goto out;
3742 
3743 	if (target)
3744 		shrink_dcache_parent(new_dentry);
3745 	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3746 	if (error)
3747 		goto out;
3748 
3749 	if (target) {
3750 		target->i_flags |= S_DEAD;
3751 		dont_mount(new_dentry);
3752 	}
3753 out:
3754 	if (target)
3755 		mutex_unlock(&target->i_mutex);
3756 	dput(new_dentry);
3757 	if (!error)
3758 		if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3759 			d_move(old_dentry,new_dentry);
3760 	return error;
3761 }
3762 
3763 static int vfs_rename_other(struct inode *old_dir, struct dentry *old_dentry,
3764 			    struct inode *new_dir, struct dentry *new_dentry)
3765 {
3766 	struct inode *target = new_dentry->d_inode;
3767 	int error;
3768 
3769 	error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry);
3770 	if (error)
3771 		return error;
3772 
3773 	dget(new_dentry);
3774 	if (target)
3775 		mutex_lock(&target->i_mutex);
3776 
3777 	error = -EBUSY;
3778 	if (d_mountpoint(old_dentry)||d_mountpoint(new_dentry))
3779 		goto out;
3780 
3781 	error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry);
3782 	if (error)
3783 		goto out;
3784 
3785 	if (target)
3786 		dont_mount(new_dentry);
3787 	if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
3788 		d_move(old_dentry, new_dentry);
3789 out:
3790 	if (target)
3791 		mutex_unlock(&target->i_mutex);
3792 	dput(new_dentry);
3793 	return error;
3794 }
3795 
3796 int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
3797 	       struct inode *new_dir, struct dentry *new_dentry)
3798 {
3799 	int error;
3800 	int is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
3801 	const unsigned char *old_name;
3802 
3803 	if (old_dentry->d_inode == new_dentry->d_inode)
3804  		return 0;
3805 
3806 	error = may_delete(old_dir, old_dentry, is_dir);
3807 	if (error)
3808 		return error;
3809 
3810 	if (!new_dentry->d_inode)
3811 		error = may_create(new_dir, new_dentry);
3812 	else
3813 		error = may_delete(new_dir, new_dentry, is_dir);
3814 	if (error)
3815 		return error;
3816 
3817 	if (!old_dir->i_op->rename)
3818 		return -EPERM;
3819 
3820 	old_name = fsnotify_oldname_init(old_dentry->d_name.name);
3821 
3822 	if (is_dir)
3823 		error = vfs_rename_dir(old_dir,old_dentry,new_dir,new_dentry);
3824 	else
3825 		error = vfs_rename_other(old_dir,old_dentry,new_dir,new_dentry);
3826 	if (!error)
3827 		fsnotify_move(old_dir, new_dir, old_name, is_dir,
3828 			      new_dentry->d_inode, old_dentry);
3829 	fsnotify_oldname_free(old_name);
3830 
3831 	return error;
3832 }
3833 
3834 SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname,
3835 		int, newdfd, const char __user *, newname)
3836 {
3837 	struct dentry *old_dir, *new_dir;
3838 	struct dentry *old_dentry, *new_dentry;
3839 	struct dentry *trap;
3840 	struct nameidata oldnd, newnd;
3841 	struct filename *from;
3842 	struct filename *to;
3843 	unsigned int lookup_flags = 0;
3844 	bool should_retry = false;
3845 	int error;
3846 retry:
3847 	from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
3848 	if (IS_ERR(from)) {
3849 		error = PTR_ERR(from);
3850 		goto exit;
3851 	}
3852 
3853 	to = user_path_parent(newdfd, newname, &newnd, lookup_flags);
3854 	if (IS_ERR(to)) {
3855 		error = PTR_ERR(to);
3856 		goto exit1;
3857 	}
3858 
3859 	error = -EXDEV;
3860 	if (oldnd.path.mnt != newnd.path.mnt)
3861 		goto exit2;
3862 
3863 	old_dir = oldnd.path.dentry;
3864 	error = -EBUSY;
3865 	if (oldnd.last_type != LAST_NORM)
3866 		goto exit2;
3867 
3868 	new_dir = newnd.path.dentry;
3869 	if (newnd.last_type != LAST_NORM)
3870 		goto exit2;
3871 
3872 	error = mnt_want_write(oldnd.path.mnt);
3873 	if (error)
3874 		goto exit2;
3875 
3876 	oldnd.flags &= ~LOOKUP_PARENT;
3877 	newnd.flags &= ~LOOKUP_PARENT;
3878 	newnd.flags |= LOOKUP_RENAME_TARGET;
3879 
3880 	trap = lock_rename(new_dir, old_dir);
3881 
3882 	old_dentry = lookup_hash(&oldnd);
3883 	error = PTR_ERR(old_dentry);
3884 	if (IS_ERR(old_dentry))
3885 		goto exit3;
3886 	/* source must exist */
3887 	error = -ENOENT;
3888 	if (!old_dentry->d_inode)
3889 		goto exit4;
3890 	/* unless the source is a directory trailing slashes give -ENOTDIR */
3891 	if (!S_ISDIR(old_dentry->d_inode->i_mode)) {
3892 		error = -ENOTDIR;
3893 		if (oldnd.last.name[oldnd.last.len])
3894 			goto exit4;
3895 		if (newnd.last.name[newnd.last.len])
3896 			goto exit4;
3897 	}
3898 	/* source should not be ancestor of target */
3899 	error = -EINVAL;
3900 	if (old_dentry == trap)
3901 		goto exit4;
3902 	new_dentry = lookup_hash(&newnd);
3903 	error = PTR_ERR(new_dentry);
3904 	if (IS_ERR(new_dentry))
3905 		goto exit4;
3906 	/* target should not be an ancestor of source */
3907 	error = -ENOTEMPTY;
3908 	if (new_dentry == trap)
3909 		goto exit5;
3910 
3911 	error = security_path_rename(&oldnd.path, old_dentry,
3912 				     &newnd.path, new_dentry);
3913 	if (error)
3914 		goto exit5;
3915 	error = vfs_rename(old_dir->d_inode, old_dentry,
3916 				   new_dir->d_inode, new_dentry);
3917 exit5:
3918 	dput(new_dentry);
3919 exit4:
3920 	dput(old_dentry);
3921 exit3:
3922 	unlock_rename(new_dir, old_dir);
3923 	mnt_drop_write(oldnd.path.mnt);
3924 exit2:
3925 	if (retry_estale(error, lookup_flags))
3926 		should_retry = true;
3927 	path_put(&newnd.path);
3928 	putname(to);
3929 exit1:
3930 	path_put(&oldnd.path);
3931 	putname(from);
3932 	if (should_retry) {
3933 		should_retry = false;
3934 		lookup_flags |= LOOKUP_REVAL;
3935 		goto retry;
3936 	}
3937 exit:
3938 	return error;
3939 }
3940 
3941 SYSCALL_DEFINE2(rename, const char __user *, oldname, const char __user *, newname)
3942 {
3943 	return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
3944 }
3945 
3946 int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
3947 {
3948 	int len;
3949 
3950 	len = PTR_ERR(link);
3951 	if (IS_ERR(link))
3952 		goto out;
3953 
3954 	len = strlen(link);
3955 	if (len > (unsigned) buflen)
3956 		len = buflen;
3957 	if (copy_to_user(buffer, link, len))
3958 		len = -EFAULT;
3959 out:
3960 	return len;
3961 }
3962 
3963 /*
3964  * A helper for ->readlink().  This should be used *ONLY* for symlinks that
3965  * have ->follow_link() touching nd only in nd_set_link().  Using (or not
3966  * using) it for any given inode is up to filesystem.
3967  */
3968 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
3969 {
3970 	struct nameidata nd;
3971 	void *cookie;
3972 	int res;
3973 
3974 	nd.depth = 0;
3975 	cookie = dentry->d_inode->i_op->follow_link(dentry, &nd);
3976 	if (IS_ERR(cookie))
3977 		return PTR_ERR(cookie);
3978 
3979 	res = vfs_readlink(dentry, buffer, buflen, nd_get_link(&nd));
3980 	if (dentry->d_inode->i_op->put_link)
3981 		dentry->d_inode->i_op->put_link(dentry, &nd, cookie);
3982 	return res;
3983 }
3984 
3985 int vfs_follow_link(struct nameidata *nd, const char *link)
3986 {
3987 	return __vfs_follow_link(nd, link);
3988 }
3989 
3990 /* get the link contents into pagecache */
3991 static char *page_getlink(struct dentry * dentry, struct page **ppage)
3992 {
3993 	char *kaddr;
3994 	struct page *page;
3995 	struct address_space *mapping = dentry->d_inode->i_mapping;
3996 	page = read_mapping_page(mapping, 0, NULL);
3997 	if (IS_ERR(page))
3998 		return (char*)page;
3999 	*ppage = page;
4000 	kaddr = kmap(page);
4001 	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
4002 	return kaddr;
4003 }
4004 
4005 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
4006 {
4007 	struct page *page = NULL;
4008 	char *s = page_getlink(dentry, &page);
4009 	int res = vfs_readlink(dentry,buffer,buflen,s);
4010 	if (page) {
4011 		kunmap(page);
4012 		page_cache_release(page);
4013 	}
4014 	return res;
4015 }
4016 
4017 void *page_follow_link_light(struct dentry *dentry, struct nameidata *nd)
4018 {
4019 	struct page *page = NULL;
4020 	nd_set_link(nd, page_getlink(dentry, &page));
4021 	return page;
4022 }
4023 
4024 void page_put_link(struct dentry *dentry, struct nameidata *nd, void *cookie)
4025 {
4026 	struct page *page = cookie;
4027 
4028 	if (page) {
4029 		kunmap(page);
4030 		page_cache_release(page);
4031 	}
4032 }
4033 
4034 /*
4035  * The nofs argument instructs pagecache_write_begin to pass AOP_FLAG_NOFS
4036  */
4037 int __page_symlink(struct inode *inode, const char *symname, int len, int nofs)
4038 {
4039 	struct address_space *mapping = inode->i_mapping;
4040 	struct page *page;
4041 	void *fsdata;
4042 	int err;
4043 	char *kaddr;
4044 	unsigned int flags = AOP_FLAG_UNINTERRUPTIBLE;
4045 	if (nofs)
4046 		flags |= AOP_FLAG_NOFS;
4047 
4048 retry:
4049 	err = pagecache_write_begin(NULL, mapping, 0, len-1,
4050 				flags, &page, &fsdata);
4051 	if (err)
4052 		goto fail;
4053 
4054 	kaddr = kmap_atomic(page);
4055 	memcpy(kaddr, symname, len-1);
4056 	kunmap_atomic(kaddr);
4057 
4058 	err = pagecache_write_end(NULL, mapping, 0, len-1, len-1,
4059 							page, fsdata);
4060 	if (err < 0)
4061 		goto fail;
4062 	if (err < len-1)
4063 		goto retry;
4064 
4065 	mark_inode_dirty(inode);
4066 	return 0;
4067 fail:
4068 	return err;
4069 }
4070 
4071 int page_symlink(struct inode *inode, const char *symname, int len)
4072 {
4073 	return __page_symlink(inode, symname, len,
4074 			!(mapping_gfp_mask(inode->i_mapping) & __GFP_FS));
4075 }
4076 
4077 const struct inode_operations page_symlink_inode_operations = {
4078 	.readlink	= generic_readlink,
4079 	.follow_link	= page_follow_link_light,
4080 	.put_link	= page_put_link,
4081 };
4082 
4083 EXPORT_SYMBOL(user_path_at);
4084 EXPORT_SYMBOL(follow_down_one);
4085 EXPORT_SYMBOL(follow_down);
4086 EXPORT_SYMBOL(follow_up);
4087 EXPORT_SYMBOL(get_write_access); /* nfsd */
4088 EXPORT_SYMBOL(lock_rename);
4089 EXPORT_SYMBOL(lookup_one_len);
4090 EXPORT_SYMBOL(page_follow_link_light);
4091 EXPORT_SYMBOL(page_put_link);
4092 EXPORT_SYMBOL(page_readlink);
4093 EXPORT_SYMBOL(__page_symlink);
4094 EXPORT_SYMBOL(page_symlink);
4095 EXPORT_SYMBOL(page_symlink_inode_operations);
4096 EXPORT_SYMBOL(kern_path);
4097 EXPORT_SYMBOL(vfs_path_lookup);
4098 EXPORT_SYMBOL(inode_permission);
4099 EXPORT_SYMBOL(unlock_rename);
4100 EXPORT_SYMBOL(vfs_create);
4101 EXPORT_SYMBOL(vfs_follow_link);
4102 EXPORT_SYMBOL(vfs_link);
4103 EXPORT_SYMBOL(vfs_mkdir);
4104 EXPORT_SYMBOL(vfs_mknod);
4105 EXPORT_SYMBOL(generic_permission);
4106 EXPORT_SYMBOL(vfs_readlink);
4107 EXPORT_SYMBOL(vfs_rename);
4108 EXPORT_SYMBOL(vfs_rmdir);
4109 EXPORT_SYMBOL(vfs_symlink);
4110 EXPORT_SYMBOL(vfs_unlink);
4111 EXPORT_SYMBOL(dentry_unhash);
4112 EXPORT_SYMBOL(generic_readlink);
4113